Emergency contraceptives

So, my last period began on August 13th & ended on the 19th which is my normal 6 day cycle. I usually go around 28 days between each period & according to this app my fertile window began on the 24th & will last to the 30th, with today being day 14 on my cycle. I had unprotected sex & my boyfriend came in me on the 25th & I took a plan b, but I have read online since that they are little to no effectiveness around the time of ovulation. I’m just trying to figure out if that statement is true, because I’m not sure honestly when my ovulation day is for sure.