A warning about Bitfinex stops

I was playing around yesterday with a few buck on Bitfinex. I decided if the price went over 6540 it would mean it would start climbing. So I placed a stop order at 6542 to see how that worked.

And as an experiment worked pretty well: I found out the order executed even though the candle does not show the price reaching the trigger level... and even the average price is so much lower that the trigger price that I can't figure out what happened.

In practical, trading terms, it is an irrelevant occurrence... but as a warning I think is rather useful.

Plus the risks I posted some time ago:
https://steemit.com/cryptocurrency/@znog/be-careful-with-stops-and-trailing-stops

Anyway, I'm trying WCEX (note that's a referral link.. but won't hurt you to use it) for a lower fees (0.1% for maker and taker... and get refunded for makers order, so that makers pay 0%... eventually ). We small traders have to pay bigger fees than those that trade larges amounts of money.