Yep, I clearly understand how to limit orders works in ideal case. My question was about unusual case which can be handled ambiguously..
What do you mean? Can you elaborate on the time you got the unusual case as you have said? Unless there is some glitch or bad connection on your end, you might see the old price and think the price hasn't hit @19100 yet. I traded and saw a fair amount of time where my orders were behind the price I saw on the order list like that. Especially on exchanges which poor connection and server-side lagging. Or when the market is packed with traders trading, things easily go haywire.