Originally Posted by
atomic sagebrush
It's not confusing really, it's simply that everyone's body, in every month that passes, is different. The surge is not "ovulation will certainly be coming at this point in time". It's more of a message that your body sends to itself of "sometime in the near future might be a great time to ovulate" and then your body does that on its own timeline. 24-36 hours is the norm; while some sources say 8-12 hours I find that is more often in people who are not consistently using OPK. Far, far more people will ovulate more like 48 to even 72 hours after that first pos than will O 8-12 hours after.
I cannot look at anyone's OPK and tell when they ovulated. The OPK are good for what they are but they're really not telling us specifically when ovulation will or did happen.
Ovulation could have been CD 13 or 14 (or even possibly not happened till later.) We just can't tell from the OPK because you can have a dark positive even after ovulation or have a test that's gone negative before O even occurs. The surge is just a signal your body sends to itself to ovulate sometime soon.