Opk help!

What day do I actually ovulate on?? I take my opks twice a day around ovulation, late morning and then around 9pm usually. I've found that sometimes my surges can last for daaayyyssss and I'll have a definitely positive opk one day (both lines are the same boldness in the first photo) but the next day I get a SUPER positive opk (test line is darker than control line in second photo). Which day would I classify as my surge?? The day I got my first positive or the day the positive is the strongest?? Ps the second photo looks like it has a dye run but it's just because the test was still developing when I took the picture