Confused LMP due date V Scan Due date

I wonder if someone can help me, I went for my 11 wk 6 day scan on Wednesday (this is based on my first day of my LMP being 2nd June) they have given me a Gestational age of 12 weeks 2 days but this would date me back to the 30th of May 3 days before my LMP even started! I'm very confused. How do they calculate this? I did tell them my LMP date, just not sure who this would be possible. Any ideas would be greatly appreciated as I have been googling all morning and just getting more confused haha! X