I too was a little worried with my emergancy u/s, when i had the scan i was supposed to be 10wks 1 day and they said 9wks 4days (which is 6days difference), but the guy doing the u/s said not to worry that my next u/s will say something different and that b/cos bubs had a really nice strong h/b that everything looked good. And each pg is different!
I am sure that is the case for you too and everything is fine. Goodluck