Please please comment! Is this App wrong? Freaking out!!!

I just realized that the ovulation day this app sets is the not the same as the normal calculation. I have a 25 day cycle and I tried calculating it on my own as well as on many ovulation date calculating websites and all of them suggest that mg actual ovulation date is two days prior that the day this App is suggesting and the I went and saw all my previous cycles and this App is always two days later than what other websites predict.

I don’t understand! I am freaking out because I had unprotected sex two days before my ovulation (according to this app), and took a plan B pill, but if this app is wrong it would mean that I had sex on my actual ovulation date and the pill won’t work if I had started ovulating.