Been back dated in pregnancy

Kara • Wed, Jul 31

So today will have put me at 8 weeks but I had a scan done by the early pregnancy unit yesterday and they said I’m looking more 7W 3D (yesterday) has this ever happened to anyone else and it be wrong ?.. my start date of period was 5th June and it lasted 6 days but my length between 28/33 days so have I just ovulated late xxx