Reply To: Cart Icon – Number of items

The theme only displays the cart quantity provided by the WooCommerce get_cart_contents_count function.

Looking at the WooCommerce php files, this is the full function:

public function get_cart_contents_count() {
    return apply_filters( 'woocommerce_cart_contents_count', array_sum( wp_list_pluck( $this->get_cart(), 'quantity' ) ) );
}

This function is filterable with the woocommerce_cart_contents_count filter, which means that you can create your own function to output a number based on your own formula, like so:

function tronds_cart_quantity() {
    /* your formula/calculations of cart quantity here */
}
add_filter( 'woocommerce_cart_contents_count', 'tronds_cart_quantity' );

Any php functions such as this should be added to the functions.php file of a child theme.