Modify the Order Length for Table Rate Shipping Settings

betrs-modify-order-length.php

/*
 * Recalculate the order's length to ignore multiple quantities.
 *
 * Requires Table Rate Shipping 4.2+
 */
function betrs_modify_calculated_length( $calculated_totals, $items ){
    // ensure there are items in the cart
    if( is_array( $items ) ) {
        $length = 0;

        // find length for items
        foreach( $items as $key => $item ) {
            $length += floatval( $item['data']->get_length() );
        }

        // change calculated length
        $calculated_totals['length'] = $length;
    }
    
    return $calculated_totals;
}
add_filter( 'betrs_calculated_totals-per_order', 'betrs_modify_calculated_length', 10, 2 );