Has anyone used the free freight threshold limits that are connected between the customer record > commercial > freight  invoicing and the carrier > management > free freight threshold settings.

I set a customer to use a threshold for a carrier, and set a threshold at the carrier... but I'm not seeing the free freight translated to my invoice.  I don't see how I can tie this to an invoicing element, and I haven't see any parameters that are applicable.  Unsure what I have to set up to get this function to work.