It was not far ahead, I just improved the ask at a time the market was slow and saw 10 lots getting filled before my 2 lots.
On ICE website, they claim to use FIFO algorythm "most of the times" or something like that. I don't remember the exact sentence.
It can be a spread order or some hidden liquidity( like on cbot )or an another algorythm used at the time... I don't know I would just like to be aware of it for the next time I trade.