Upgrade Coupon Question

[allieoop]

I have a coupon for a 2 car class upgrade for National from the Entertainment Book. Has anyone booked this on the National website before? If I want a full-size car, do I book a full-size or a compact? I chose a compact but on the final reservation page it still shows "compact". I guess my question is should the reservation show compact but when I get to the EA I pick out a full-size and give them the upgrade coupon when I drive through the check-out? I know this question doesn't make a lot of sense, but I think I've been on their website so long trying to figure this out that I've confused myself.