This is my first month really temping (oral). I started middle of last month so not sure it counted. I wanted to chart to make sure that I am ovulating and see if I can identify the window. So I am relieved to see that I do have a definitely shift here.

But I want to understand WHY this chart (set to advanced) is suggesting that I ovulated on day 19 and NOT day 21? I know OPK (ovulation predictor kit) was last positive on 19 but you can ovulate 2-3 days after surge to my knowledge.

There are open dots because I sometimes woke up before or after my usual time of 745am. I always had regular periods between 30-34 days though last month it was a weird 28. And I did also have one cycle about 2-3 months ago that was 18 days but that's out of ordinary for me. I don't have PCOS or any medical issues at all.

Chart at this link: