Vaughan,
I think I maybe misunderstood what you wanted. If you wanted a train that entered the portal to come out loaded, then you must use the "Consume Trains" option, then select "Train returns after 5 mins delay", then you get the 5 options I stated above.
If you just want to produce a train you have to choose which train is coming out, then as Shane says in the Driver instructions, select Instant Load. Hope that clarifies the situation.
Regards,
Dave