Plan B

I had unprotected sex about 2-3 weeks ago now, I took the ful dosage (1.5) or whatever it is and it says it's suppose to delay your period, I'm suppose to get it this week it's one day late. I'm just wondering how long it's suppose to delaying for exactly cause I guess it's different with the full dosage. (added on: I forgot to mention I had my
period, heavy right after the pill maybe a couple days after. would that count as my period or no?)