Didnt tell me due date 6 1/2 wks

An
So because I have irregular periods (53 days last time I had one) I thought I was 9 weeks 1 day but it turns out during my ultrasound I was 6 1/2 weeks he said, I'm not sure if that means I was 6w 3d or 6w 4d (this was yesterday) but is anyone else 6 1/2 weeks and what would the due date be