Only market makers see AON (All or nothing bids) on level 3, lets say you have AON order for 7000 shares sitting at 17, someone or a market makers decides to sell 6000 shares at 16, you order at 17 will get skipped to 16, but if they decided to sell 7500 to at 16 cents, your order will get executed, plus the 500 shares at 16.