Why did Glow change my O date?

Shay

Positive OPK yesterday. Glow predicted ovulation today. I had all the signs, EWCM- ovulatory pain (yes I am familiar enough with my body to know this was it) and I expect my temp to have risen when I temp in the morning. I also took an OPK today just to see if I still had a surge - I didn’t- so glow changed my O date to yesterday. Why?? I could still have ovulated today with a negative opk today correct?