Time in Force - OPG - Filled Price != Open Price


I placed the following order:
place_order(symbol=“AAPL”, qty=5, side=“buy”, type=“market”, time_in_force=“opg”)

The order was filled at 2020-06-24T13:30:07.27345Z, with price $365.83, which is much higher than the true open price $365.05 at 24 Jun, 2020.

could anyone explain why? is there a fee during open auction period?

Also a bit confused that the order was filled after open auction period, but it is less critical.