Let me start by telling you I'm NOT using Autoexecute
I do trade with AF and use J-Trader
I think they work the same as the J-Trader MEL function.
The order is send upon reaching a price point. (Can be set on BID / ASK and also size can be taken into calculations) BUT, if you decide to send your orders as limit (only possible option so far in J-Trader)
THIS DOES NOT GARANTEE A FILL !!!
This is why you have to stay at your screen.
If your orders can be send as MARKET (when conditions are met), you get a garanteed fill but off course no garanteed price.
So keep in mind, if the price action is pretty fast, you might not get an execution. (No problem , software noticed this also)
Only problem is, is you trade multiple different contracts at the same time which are triggered upon each others price action, you might get a fill on one contract and not on the other. You than have to manually adjust the order for a fill (or get lucky the price moves so it gets triggered later)
Hope this help.