Hi there just a word to the wise play around with BetAngel in sim mode first till you get used to the markets and such.
Letting horses go in play is a no no for me as you've found out, I'd have just hedged out for a small loss rather than go in play, unless you're going to trade in play that is and in which case the place market at the end of a race can certainly be your friend
Sorry I don't want this to sound condescending but after this community has helped me, I'd though I try to help a little back.