Add number of items in cart to WooCommerce menu item

gistfile1.txt

function custom_wc_cart_link() {
    ob_start();
    ?>
    <a href="<?php echo esc_url( wc_get_cart_url() ); ?>" class="cart-contents">
		<?php echo sprintf ( _n( '%d', '%d', WC()->cart->get_cart_contents_count() ), WC()->cart->get_cart_contents_count() ); ?>
		<span class="amount"><?php echo wp_kses_data( WC()->cart->get_cart_subtotal() ); ?></span>
	</a>
    <?php
    return ob_get_clean();
}

remove_filter( 'wp_nav_menu_items','generatepress_wc_menu_cart', 10, 2 );

add_filter( 'wp_nav_menu_items', function( $nav, $args ) {
    if ( $args->theme_location == 'primary' && generatepress_wc_get_setting( 'cart_menu_item' ) ) {
        return sprintf(
            '%1$s
            <li class="wc-menu-item %4$s" title="%2$s">
                %3$s
            </li>',
            $nav,
            esc_attr__( 'View your shopping cart','generate-woocommerce' ),
            custom_wc_cart_link(),
            is_cart() ? 'current-menu-item' : ''
        );
    }

    return $nav;
}, 10, 2 );

add_filter( 'woocommerce_add_to_cart_fragments', function( $fragments ) {
	ob_start();
	?>
	<a href="<?php echo esc_url( wc_get_cart_url() ); ?>" class="cart-contents">
		<?php echo sprintf ( _n( '%d', '%d', WC()->cart->get_cart_contents_count() ), WC()->cart->get_cart_contents_count() ); ?>
		<span class="amount"><?php echo wp_kses_data( WC()->cart->get_cart_subtotal() ); ?></span>
	</a>
	<?php
	$fragments['a.cart-contents'] = ob_get_clean();

	return $fragments;
} );

Sorry, but what exactly is this code for ? Thanks.