When you put an order in, it gets sent to a MM. S
Post# of 148207
30k at 90c
20k at 87c (your order).
CSTI will only show the top bid, 30k at 90c. When that order gets hit, someone sells 30k at 90c and your order becomes the top order, it takes the MM some time to reset to your order, sometimes as long as 10 seconds before your order will show on l2. During that time while your MM resets the top bidder, shares can be sold to other market makers at a lower price. That is very likely what happened, especially since it was just a blip a couple second drop to 83c. Now if someone had 83c on the ask for say 30 seconds and your order didn't get filled, I would be upset.