Ovulation help..!

Hi! So this is my second cycle with using OPKs and charting ... Well I'm still a little confused by the OPKs especially the strips.. Well AF came on 07-17 and ended 07-21 according to Glow I should've ovulated on the 30th...

So I'm going to post some pics below each has the date of the day I took it. Can someone please help me figure out what's what .. Lol

On the 30th I took one in the AM and one in the evening ... But I don't get why they're so up and down ..