So, I had a few shares of MO shorted. Last night I made two OCO (one cancels other) orders on TOS. The orders were: Buy +13 MO stop at $78.50 Buy +13 MO stop at $81.00 They were both GTC orders, but I came home today and saw that the first order was filled at 9:30:17 even though MO never went low enough to hit $78.50. The order was filled with MO at $80.40. What's going on here? I thought the stop order changes into a market order when the price of the stock hits the stop.