LH surge question

RM 💕 | IVF Baby Due Feb. 2020 🤰

How long are typical surges? I use OPKs (don’t temp) and I got what I thought was a positive on the 9th

(Two tests taken at the same time because one was so faint)

Anyway - I kept testing like a nerd (and I have 100+ of these so why not) and I got a negative in the afternoon of the 10th. That night, a positive.

This was the test I took about 10min a go:

How long are surges typically??? I thought I would have ovulated on the 10th. Do OPKs immediately go negative upon ovulation?

Should I count the tests from the 9th as the first positive and just count up to 36hrs as my ovulation? Confused! Haha.