I'm not sure if this is the right thread, but can anyone tell me how PC upgrades are supposed to work? I am PC and booked a "Cadillac XT5 or similar" which I think is Group H? What does that mean a two group "upgrade" would be? I don't think I totally understand what that means. I'm driving around a bunch with my father-in-law so would like a nicer car, but don't want/need a huge car (last time I rented with Avis they "upgraded" me to an Infiniti QX80 and that thing drove like a tank), but am bringing my golf clubs so want to make sure I have an SUV.

It's somewhat confusing, so any help would be great!