When 10% trades have MAE 7, the optimization result is unknown. When we assume that 100% trades have MAE of exactly 7, the optimized Entry is -7. The trade would then be filled at current price - 7 + Penalty. Since Penalty applies to all trades, it has no effect on the optimization. You would then set the live order limit at Entry + Penalty, because that is the fill price that you get from the broker. The live result will then match the backtest. The specified Penalty is your overshoot.