8 weeks 5 days scan

Oh just to.add, i am.measuring 2 days ahead so i am supposed to.be 8 weeks 3 days but i am 8 weeks 5 day. I went in for a rescan this morning and baby had heartrate of 171 and everything looked good. When i went back through my notes, it says my yolk sac is 7.3mm but from reading online it shouldnt be any bigger than 6mm. The sonographer didnt say anything about it but has anyone else expect having a large yolk sac and having a healthy pregnancy. This is my second one