Increase the maximum party size displayed in the settings.

increase-max-party-size-option-for-rtb.php

<?php
/**
 * Plugin Name: Increase Party Size Options for Restaurant Reservations
 * Plugin URI: http://themeofthecrop.com
 * Description: Increase the maximum party size displayed in the settings.
 * Version: 0.0.1
 * Author: Theme of the Crop
 * Author URI: http://themeofthecrop.com
 * License:     GNU General Public License v2.0 or later
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 *
 * 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.
 *
 * 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 St, Fifth Floor, Boston, MA 02110-1301 USA
 */
if ( ! defined( 'ABSPATH' ) )
	exit;

add_filter( 'rtb_party_size_upper_limit', 'rtbmps_increase_party_size_options', 10 );
function rtbmps_increase_party_size_options( $max ) {
	return 200;
}