ovulation tests

This is the first time I have used the ovulation tests, according to the glow app I am in my fertile window up to tomorrow so I have been doing tests every day since Monday waiting for my surge. I normally test around 5 o'clock as the test say to do it in the afternoon. But when I do the test is takes about 5 seconds for the test line to appear but then after about 5 minutes a second faint line appears. Is this normal? I came off the pill after 10 years in January and I have been using the app since June and I thought the tests might help pin point exactly when we need to do the deed, but I am just very confused.