Worried about ultrasound

So I had my 12 weeks ultrasound checkup the other day (I was 12 weeks and 5 days) and I get to watch the whole thing so I noticed on the screen it said EDD (estimated due date) 12 wks 5 dys but underneath it said AVG 13 weeks 2 days. I have no clue what this means and I'm kinda worried haha. The ultrasound tech can't answer questions either. Anyone know what this means??