Confused by ovulation tests🙃

I have been taking ovulation test for the past few days and usually I read them after a few minutes. I saved them and I’m wondering if the results change after a few days or what? I scan them on two apps after I take them to compare. I’m feel kind of confused🙃 can anyone help?? I use the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> & Premom which was recommended by Easy@Home, the other one I just downloaded is ‘Femometer’ just to scan the tests some where else!