The Cancel All Unmatched Bets in Market is no good for this because if just 1p is matched it's counted as a matched bet and any unfilled amount gets cancelled along with all the others when another bet gets 1p (or more) matched … so you can end up with 2 bets of 1p each!
I therefore went to Cancel Unmatched Bets on Selection. I looped through Any Selection and set conditions such that the selection's bets were cancelled if the number of matched bets in the market was >1 and the number of matched bets on the selection was = 0 thinking that met my conditions … but no.
I am attaching a zip of the Market Reports and a screen grab of the Automation panel in Guardian created by the included .baf. The Lay All rule is just a convenient simple substitute for my bet selection criteria. Note here three bets were matched but with ample time to have cancelled the 3rd before matched. Also it would seem that only one bet in all was actually cancelled, I assume the others just lapsed. Now I'm sure I can achieve my want by setting signals as bets are detected as matched but as part of my learning process I'm curious why my logic is not working.
Ignore the Signal set for one runner, that is a relic from my full rule set when I switched to a Lay All rule for this example.
… I'm still using Cancel Unmatched Bets by Selection but instead of using the Number of Unmatched Bets condition on the Selection = 0, I am using Unmatched Bets Amounts condition where the Unmatched Lay Bets Amount on the Selection is equal to [the stake] i.e. none has been matched yet. That works perfectly … don't know why the original doesn't work though!