Just read a nice piece on the AP for the A320 And I notice on the left lower corner there is the letters QNH. Is it some type of setting a little up and to the right it is above a dial?
QNH is the local airport pressure which is set to 1013 at the moment but can be adjusted with the knobs in the glareshield. Primarily this just adjusts the altimeters for the differences in pressure due to high or low pressure weather systems, which are not modeled in Aerofly at the moment. So this is more for the future.
The autopilot isn't really affected by this, its not an flight guidance control knob in the first place. It just means that your altimeters are calibrated differently and thus the autopilot will receive different altitude information but still maintains the altitude seen on the primary flight display.