how to add limit List Custom Taxonomy Widget Wordpress?

<?php
/**
 * Plugin Name: List Custom Taxonomy Widget
 * Plugin URI: http://celloexpressions.com/plugins/list-custom-taxonomy-widget
 * Description: Widget that displays category listings for custom post types (custom taxonomies).
 * Version: 4.1
 * Author: Nick Halsey
 * Author URI: http://celloexpressions.com/
 * Tags: custom taxonomy, custom tax, widget, sidebar, category, categories, taxonomy, custom category, custom categories, post types, custom post types, custom post type categories
 * License: GPL
 
=====================================================================================
Copyright (C) 2016 Nick Halsey

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
=====================================================================================
*/

// Register 'List Custom Taxonomy' widget
add_action( 'widgets_init', 'init_lc_taxonomy' );
function init_lc_taxonomy() { return register_widget('lc_taxonomy'); }

class lc_taxonomy extends WP_Widget {
    /** constructor */
    function __construct() {
        parent::__construct( 'lc_taxonomy', $name = 'List Custom Taxonomy', array(
            'customize_selective_refresh' => true,
        ) );
    }

    /**
    * This is the Widget
    **/
    function widget( $args, $instance ) {
        global $post;
        extract($args);

        // Widget options
        if ( array_key_exists( 'title', $instance ) ) {
            $title = apply_filters('widget_title', $instance['title'] ); // Title
        } else {
            $title = '';
        }
        if ( array_key_exists( 'taxonomy', $instance ) ) {
            $this_taxonomy = $instance['taxonomy']; // Taxonomy to show
        } else {
            $this_taxonomy = '';
        }
        $hierarchical = !empty( $instance['hierarchical'] ) ? '1' : '0';
        $inv_empty = !empty( $instance['empty'] ) ? '0' : '1'; // invert to go from UI's "show empty" to WP's "hide empty"
        $showcount = !empty( $instance['count'] ) ? '1' : '0';
        if( array_key_exists('orderby',$instance) ){
            $orderby = $instance['orderby'];
        }
        else{
            $orderby = 'count';
        }
        if( array_key_exists('ascdsc',$instance) ){
            $ascdsc = $instance['ascdsc'];
        }
        else{
            $ascdsc = 'desc';
        }
        if( array_key_exists('exclude',$instance) ){
            $exclude = $instance['exclude'];
        }
        else {
            $exclude = '';
        }
        if( array_key_exists('childof',$instance) ){
            $childof = $instance['childof'];
        }
        else {
            $childof = '';
        }
        if( array_key_exists('dropdown',$instance) ){
            $dropdown = $instance['dropdown'];
        }
        else {
            $dropdown = false;
        }
        // Dropdown doesn't work for built-in taxonomies.
        $builtin = array( 'post_tag', 'post_format', 'category' );
        if ( $dropdown && in_array( $this_taxonomy, $builtin ) ) {
            $dropdown = false;
        }
        // Output
        $tax = $this_taxonomy;
        echo $before_widget;
        echo '<div id="lct-widget-'.$tax.'-container" class="list-custom-taxonomy-widget">';
        if ( $title ) echo $before_title . $title . $after_title;
        if($dropdown){
            $taxonomy_object = get_taxonomy( $tax );
            if( in_array( $tax, array( 'category', 'post_tag', 'post_format' ) ) )
                $walker = '';
            else
                $walker = new lctwidget_Taxonomy_Dropdown_Walker();
            $args = array(
                'show_option_all'    => false,
                'show_option_none'   => '',
                'orderby'            => 'RANDOM()',//$orderby,
                'order'              => $ascdsc,
                'show_count'         => $showcount,
                'hide_empty'         => $inv_empty,
                'child_of'           => $childof,
                'exclude'            => $exclude,
                'echo'               => 1,
                //'selected'           => 0,
                'hierarchical'       => $hierarchical,
                'name'               => $taxonomy_object->query_var,
                'id'                 => 'lct-widget-'.$tax,
                //'class'              => 'postform',
                'depth'              => 0,
                //'tab_index'          => 0,
                'taxonomy'           => $tax,
                'hide_if_empty'      => true,
                'walker'            => $walker,
            );
            echo '<form action="'. get_bloginfo('url'). '" method="get">';
            wp_dropdown_categories($args);
            echo '<input type="submit" value="go &raquo;" /></form>';
        }
        else {
            $args = array(
                    'show_option_all'    => false,
                    'orderby'            => $orderby,
                    'order'              => $ascdsc,
                    'style'              => 'list',
                    'show_count'         => $showcount,
                    'hide_empty'         => $inv_empty,
                    'use_desc_for_title' => 1,
                    'child_of'           => $childof,
                    //'feed'               => '',
                    //'feed_type'          => '',
                    //'feed_image'         => '',
                    'exclude'            => $exclude,
                    //'exclude_tree'       => '',
                    //'include'            => '',
                    'hierarchical'       => $hierarchical,
                    'title_li'           => '',
                    'show_option_none'   => 'No Categories',
                    'number'             => null,
                    'echo'               => 1,
                    'depth'              => 0,
                    //'current_category'   => 0,
                    //'pad_counts'         => 0,
                    'taxonomy'           => $tax,
                    'walker'             => null
                );
            echo '<ul id="lct-widget-'.$tax.'">';
            wp_list_categories($args);
            echo '</ul>';
        }
        echo '</div>';
        echo $after_widget;
    }
    /** Widget control update */
    function update( $new_instance, $old_instance ) {
        $instance = $old_instance;
        
        $instance['title']  = strip_tags( $new_instance['title'] );
        $instance['taxonomy'] = strip_tags( $new_instance['taxonomy'] );
        $instance['orderby'] = $new_instance['orderby'];
        $instance['ascdsc'] = $new_instance['ascdsc'];
        $instance['exclude'] = $new_instance['exclude'];
        $instance['expandoptions'] = $new_instance['expandoptions'];
        $instance['childof'] = $new_instance['childof'];
        $instance['hierarchical'] = !empty($new_instance['hierarchical']) ? 1 : 0;
        $instance['empty'] = !empty($new_instance['empty']) ? 1 : 0;
        $instance['count'] = !empty($new_instance['count']) ? 1 : 0;
        $instance['dropdown'] = !empty($new_instance['dropdown']) ? 1 : 0;

        return $instance;
    }
    
    /**
    * Widget settings
    **/
    function form( $instance ) {
        //for showing/hiding advanced options; wordpress moves this script to where it needs to go
            wp_enqueue_script('jquery');
            ?><script>
            jQuery(document).ready(function(){
                var status = jQuery('#<?php echo $this->get_field_id('expandoptions'); ?>').val();
                if ( status === 'expand' ) {
                    jQuery('.lctw-expand-options').hide();
                    jQuery('.lctw-all-options').show();
                } else {
                    jQuery('.lctw-all-options').hide();
                }
            });
            function lctwExpand(id){
                jQuery('#' + id).val('expand');
                jQuery('.lctw-all-options').show(500);
                jQuery('.lctw-expand-options').hide(500);
            }
            function lctwContract(id){
                jQuery('#' + id).val('contract');
                jQuery('.lctw-all-options').hide(500);
                jQuery('.lctw-expand-options').show(500);
            }
            </script><?php
          // instance exist? if not set defaults
            if ( $instance ) {
                $title  = $instance['title'];
                $this_taxonomy = $instance['taxonomy'];
                $orderby = $instance['orderby'];
                $ascdsc = $instance['ascdsc'];
                $exclude = $instance['exclude'];
                $expandoptions = $instance['expandoptions'];
                $childof = $instance['childof'];
                $showcount = isset($instance['count']) ? (bool) $instance['count'] :false;
                $hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
                $empty = isset( $instance['empty'] ) ? (bool) $instance['empty'] : false;
                $dropdown = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
            } else {
                //These are our defaults
                $title  = '';
                $orderby  = 'count';
                $ascdsc  = 'desc';
                $exclude  = '';
                $expandoptions  = 'contract';
                $childof  = '';
                $this_taxonomy = 'category';//this will display the category taxonomy, which is used for normal, built-in posts
                $hierarchical = true;
                $showcount = true;
                $empty = false;
                $dropdown = false;
            }
            
        // The widget form ?>
            <p>
                <label for="<?php echo $this->get_field_id('title'); ?>"><?php echo __( 'Title:' ); ?></label>
                <input id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo $title; ?>" class="widefat" />
            </p>
            <p>
                <label for="<?php echo $this->get_field_id('taxonomy'); ?>"><?php echo __( 'Select Taxonomy:' ); ?></label>
                <select name="<?php echo $this->get_field_name('taxonomy'); ?>" id="<?php echo $this->get_field_id('taxonomy'); ?>" class="widefat" style="height: auto;" size="4">
            <?php
            $args=array(
              'public'   => true,
              '_builtin' => false //these are manually added to the array later
            );
            $output = 'names'; // or objects
            $operator = 'and'; // 'and' or 'or'
            $taxonomies=get_taxonomies($args,$output,$operator);
            $taxonomies[] = 'category';
            $taxonomies[] = 'post_tag';
            $taxonomies[] = 'post_format';
            foreach ($taxonomies as $taxonomy ) { ?>
                <option value="<?php echo $taxonomy; ?>" <?php if( $taxonomy == $this_taxonomy ) { echo 'selected="selected"'; } ?>><?php echo $taxonomy;?></option>
            <?php }    ?>
            </select>
            </p>
            <h4 class="lctw-expand-options"><a href="javascript:void(0)" onclick="lctwExpand('<?php echo $this->get_field_id('expandoptions'); ?>')" >More Options...</a></h4>
            <div class="lctw-all-options">
                <h4 class="lctw-contract-options"><a href="javascript:void(0)" onclick="lctwContract('<?php echo $this->get_field_id('expandoptions'); ?>')" >Hide Extended Options</a></h4>
                <input type="hidden" value="<?php echo $expandoptions; ?>" id="<?php echo $this->get_field_id('expandoptions'); ?>" name="<?php echo $this->get_field_name('expandoptions'); ?>" />
                
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('count'); ?>" name="<?php echo $this->get_field_name('count'); ?>"<?php checked( $showcount ); ?> />
                <label for="<?php echo $this->get_field_id('count'); ?>"><?php _e( 'Show Post Counts' ); ?></label><br />
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('hierarchical'); ?>" name="<?php echo $this->get_field_name('hierarchical'); ?>"<?php checked( $hierarchical ); ?> />
                <label for="<?php echo $this->get_field_id('hierarchical'); ?>"><?php _e( 'Show Hierarchy' ); ?></label><br/>
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('empty'); ?>" name="<?php echo $this->get_field_name('empty'); ?>"<?php checked( $empty ); ?> />
                <label for="<?php echo $this->get_field_id('empty'); ?>"><?php _e( 'Show Empty Terms' ); ?></label></p>
                
                <p>
                    <label for="<?php echo $this->get_field_id('orderby'); ?>"><?php echo __( 'Order By:' ); ?></label>
                    <select name="<?php echo $this->get_field_name('orderby'); ?>" id="<?php echo $this->get_field_id('orderby'); ?>" class="widefat" >
                        <option value="ID" <?php if( $orderby == 'ID' ) { echo 'selected="selected"'; } ?>>ID</option>
                        <option value="name" <?php if( $orderby == 'name' ) { echo 'selected="selected"'; } ?>>Name</option>
                        <option value="slug" <?php if( $orderby == 'slug' ) { echo 'selected="selected"'; } ?>>Slug</option>
                        <option value="count" <?php if( $orderby == 'count' ) { echo 'selected="selected"'; } ?>>Count</option>
                        <option value="term_group" <?php if( $orderby == 'term_group' ) { echo 'selected="selected"'; } ?>>Term Group</option>
                    </select>
                </p>
                <p>
                    <label><input type="radio" name="<?php echo $this->get_field_name('ascdsc'); ?>" value="asc" <?php if( $ascdsc == 'asc' ) { echo 'checked'; } ?>/> Ascending</label><br/>
                    <label><input type="radio" name="<?php echo $this->get_field_name('ascdsc'); ?>" value="desc" <?php if( $ascdsc == 'desc' ) { echo 'checked'; } ?>/> Descending</label>
                </p>
                <p>
                    <label for="<?php echo $this->get_field_id('exclude'); ?>">Exclude (comma-separated list of ids to exclude)</label><br/>
                    <input type="text" class="widefat" name="<?php echo $this->get_field_name('exclude'); ?>" value="<?php echo $exclude; ?>" />
                </p>
                <p>
                    <label for="<?php echo $this->get_field_id('exclude'); ?>">Only Show Children of (category id)</label><br/>
                    <input type="text" class="widefat" name="<?php echo $this->get_field_name('childof'); ?>" value="<?php echo $childof; ?>" />
                </p>
                <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id('dropdown'); ?>" name="<?php echo $this->get_field_name('dropdown'); ?>"<?php checked( $dropdown ); ?> />
                <label for="<?php echo $this->get_field_id('dropdown'); ?>"><?php _e( 'Display as Dropdown' ); ?></label></p>
            </div>
<?php
    }

} // class lc_taxonomy

/* Custom version of Walker_CategoryDropdown */
class lctwidget_Taxonomy_Dropdown_Walker extends Walker {
    var $tree_type = 'category';
    var $db_fields = array ( 'id' => 'term_id', 'parent' => 'parent' );

    function start_el( &$output, $term, $depth = 0, $args = array(), $current_object_id = 0 ) {
        $term = get_term( $term, $term->taxonomy );
        $term_slug = $term->slug;

        $text = str_repeat( '&nbsp;', $depth * 3 ) . $term->name;
        if ( $args['show_count'] ) {
            $text .= '&nbsp;('. $term->count .')';
        }

        $class_name = 'level-' . $depth;

        $output.= "\t" . '<option' . ' class="' . esc_attr( $class_name ) . '" value="' . esc_attr( $term_slug ) . '">' . esc_html( $text ) . '</option>' . "\n";
    }
}
?>