Add this to the functions.php of your theme to set the dimensions of your popup to 1000 x 600 pixels and disable the popup for screens below a width of 480 pixels.

wpt_customize_tickets_lightbox.php

<?php
/**
 * Sets the dimensions of the tickets lightbox to 1000 x 600 pixels and 
 * disables the lightbox for screens below a width of 480 pixels.
 * 
 * @param	array 	$args	The default settings for the tickets lightbox.
 * @return	array			The new settings.
 */
function wpt_customize_tickets_lightbox($args) {
	$args['width'] = 1000;
	$args['height'] = 600;
	$args['disable_width'] = 480;
	return $args;
}
add_filter('wpt/frontend/thickbox/args', 'wpt_customize_tickets_lightbox');