Equate OPKs??

Ladies, do any of you use this brand of OPKs? It's my first month using any kind of ovulation tests and I decided at last minute this month to do so, so I'm thinking next month I may have better luck. Anyways, my question is with this brand after they sit over a few hours or even days do the lines for any of you guys go darker. Such as in my picture. My lines are all dark now and it confused me.