I don't have the game, but the Dualnote is indeed a hybrid so that's most probably what it is - I don't remember there being another gauge for the Prius in GT2, but GTC is a more sophisticated beast.
I'll be there by the weekend - my store finally has it in stock Wednesday. I don't know when I'll be over there to pick it up - I have, like, this house to buy, but it'll be Thursday night by the latest.