I’m on day 12 and started ovulating so I think it varies . I usually ovulate around 18
This looks positive to me. But you should keep testing to see if it gets even stronger or if it gets lighter again to know when your actual peak was. But if you didn't test more I'd just consider this your peak and assume you ovulated 12-36 hours later.
Looks like it could be but havnt seen ones before or after. You could ovulate in the next 12-36 hours