Ovulation testing

So, I've been using the Ovulation testing kits for about 12 months, and just now learned that you are supposed to be using your 2nd urine of the day - not the 1st. I guess with the first, you can get a false positive. That would have been nice to know...

I doubt its made much of a difference since we usually bd every other day starting at cd 17, but still, wish the instructions said that...