Two days ago, my chart marked O on CD16, in which case I feel good about the IUI timing. (top graph)

But this morning, I entered my (unremarkable) temp, and it changed O to CD14 (bottom graph)! I wish I hadn't missed yesterday's temp, but that can't be helped now.

One additional piece of data: At my u/s and b/w the morning of CD14, we could very clearly see a nice big follicle (23.8mm), which makes me think that FF is wrong.

I'm not freaking out because I do believe that the IUI was well-timed, but can anyone interpret this random change? Thanks!