Ovulation

So I’m new to <a href="https://play.google.com/store/apps/details?id=com.glow.android">tracking ovulation</a>. I used a opk on cycle day 17 and was ovulating. Took another just to see on cycle day 24 and it’s not positive but still there’s a line. Do you always have a line on opks? I’m a little confused. Any advice helps on how to use these things. Thanks😊

Cycle day 17

Cycle day 24