New to OPK, need help 😳

Before I start, please don’t think I’m stupid.. I’m very to you OPK and TTC.. I’m approx. CD18 (last period was early & only light spotting. Almost don’t even consider it a period) the two tests in the pic are from today. Top is from 1pm and bottom is 5pm. I’ve been doing Ovulation tests since May 15th (I try my best to do them around the same time every day), and the test from today at 1pm is the darkest I’ve gotten so far (pic looks positive but in person it’s not quite as dark as the control line) But why is 5pm lighter?? I did not pee in between tests and did not drink anything either. Thank you for not thinking I’m stupid, I will take any info/suggestions/thoughts that I can get. ❤️❤️❤️