It's just a simple rule that checks to see if the value in the quantity scanned field is equal to the required quantity value. If not equal, then it sets a checkbox flag that the field containing the IOL code is looking at to determine whether to run or not.
Honestly, the form rule isn't needed as I can set the IOL formula field to look at the scanned quantity compared to the required quantity and it would have the same result. That was the way I set it up originally but had the same problem it's having now, runs once then never triggers again.