Help! When do I start my first pack of BC?

Hey guys! So I just got prescribed birth control for the first time. It's Orsythia, so it's the combination pill (both progestin and estrogen). I'm pretty stinkin sure my doctor said to start taking it on the third day of my next period, but the directions say start it on the first day of my period or the Sunday after my period. To be honest, I am very confused. Help?!