This is postmarket. Here are the top asks arca 20.19 1000 brut 20.24 800 You place a buy order at 20.25, intelligent. You first get filled 800 shares from brut at 20.24, then the remaining shares from arca at 20.19. I know, you should place your limit order at 20.19, or go direct to arca. But assume the market is moving too fast to make that kind of decision quickly.