FTM confused about anatomy scan and baby weight estimate

Catherine
I was 20 weeks exactly but baby measured 21 weeks 3 days. They didn't alter the expected due date- my understanding is that the first trimester is the most accurate- but the baby is in the normal range for growth. I'm very happy and a little confused. Is this an indicator that I'm having a big baby? I'm 6ft, my husband is 6'7 and I was 9lbs 15oz at my birth. Or could it mean I'll deliver early?