Need help with mobile view

Hi,

I am in the process of making an online pick and mix sweet shop. I love this plugin as it gives the exact feature I need. However I am wanting to amend the mobile view so that it has 4 columns. I have added code to display 6 columns which is perfect for desktop, but could you please tell me what PHP I need to add to change to 4 columns, only for mobile view?

This is code I used for the 6 columns on desktop:

add_filter( 'woocommerce_bundled_items_grid_layout_columns', 'wc_pb_grid_layout_change_number_of_columns', 10, 2 );

function wc_pb_grid_layout_change_number_of_columns( $columns, $bundle ) {
	return 6;
}

Thank you ??

The page I need help with: [log in to see the link]