Opk help

Ughhh first time using these properly, I got them late🙃. Box of 80 turnt up today.

Done this one and tried using the part of this app to record it ;

But what if I’ve missed ovulation day? Would the lh level go down significantly after? Or could it remain high enough to give a negative but , dark neg like almost pos aghh. I know I’ll have to wait and see I just don’t know.