There is no incorrect setting.It was suggested in an earlier thread that you were considering adding some sort of "dot" or "mark" at the optimal MV setting on all of the amp models in a future FW update. I would absolutely LOVE to see this happen. I am sure all of us are guilty of incorrect MV settings on most of our presets...
I think the best the model could do would be to mimic the real amp as closely as possible.
From the prelim information, its looking like the MV and presence controls will be matching the real amps.