WP-Eventer Plugin shortcode to get remaining tickets.

ticket_count_shortcode.php

//Product Sales Shortcode
function ticket_count_shortcode( $atts ) {
    $atts = shortcode_atts( array( 'id' => null, 'count' => 0), $atts, 'bartag' );

    if( intval( $atts['id'] ) > 0 && function_exists( 'wc_get_product' ) ){ 
        $_product = wc_get_product( $atts['id'] );
        $tickets_left = $atts['count']-($_product->get_total_sales());
      } 
  return $tickets_left; 
} 
add_shortcode( 'tickets_count', 'ticket_count_shortcode' );

Add to theme's functions.php
Usage:
[tickets_count id="xx" count="xx"]
id= Product id
count= Number of tickets issued