Glow changing my ovulation days?

Fylicia

I am still learning so please be kind. My period is now 12 days late & I noticed Glow keeps changing what my Ovulation days were for August when I log that AF hasn't shown. I haven't started tracking my BBT yet or using any OPK but it's just confusing to me. Before this month my cycle has been very regularly 28-29 days. So I guess I am confused about how many DPO I am if the dates keep moving?