When a Transport Type is selected against each container in the Container Details tab in Import Job Registration the Transport Request sent to the Carrier will contain the Delivery Code they understand in their system. The Transport Types are stored in the bottom half of the Carrier Codes Mapping tab in the Administration > Customer Masterfile for the EDI Carrier.
This screen allows the carrier to have different transport types at different ports. Expedient users will only be able to select the transport types available at the destination port for the Carrier in the Import Job Registration screen.