Help!!

So I've been having what I think is implementation bleeding. According to this app AF is supposed to be here on 8/28 but I'm pretty regular with a 28 day cycle so from my calculations that'd be 8/23. My spotting today is a brown/creamy normal CM (seems like) and really only when a wipe. Have a little on my pad but not much. So how long after do I wait? If I take one on 8/24 will it be too soon or should I wait until 8/28 to see if I get AF like glow is telling me?