I've always remembered/known it as this:
CIRCLES= filly (O for ovaries)
And by the way, that app in your avatar is B-E-A-UTIFUL!!!!!!!! Got any more pics???
That's the problem with it! Everyone says differently. So far, out of 4 "tests" and 3 foals on the ground it's been 100% back and forth with fillies. I have one more mare to foal so we'll see if it's true again. To get really deep on the topic, I wonder if the electrical activity of the foal is determined by the mare/stallion cross. Which would explain why each farm has a different signal for fillies and colts. It's for kicks and giggles anyway.Sorry, but one of you said back and for for colts and the other said back and forth for fillies. Which is it?