Disappearing line?

I don’t know if I’m to post this here or where else. I tested yesterday morning not first thing and got that darker one on the top. I just tested this morning and it looks so much lighter than the one from yesterday. Do you think it’s because it’s not dry like the one from yesterday has dried? I’m trying to give it a little and see if it’ll end up looking the same, but it’s stressing me out now.