ultrasound dating

[Annz1954]

i had a transvaginal and regular ultrasound done on the same day 10-18-2012.    they put my GA at 6w4d and the CRL was at .55cm   what i believe was my LMP was  9-2-2012.    they put my due date at 6-8-2013  My periods are generally on time (1st or 2nd of each month)  but only last for about 3 days.    i would just like some reassurance, for personal reasons, that all these figures add up and their is no way I could have conceived sometime in early/mid August

[Annz1954]

thank you!  :)

[AnnieBrooke]

For the due date of June 8, conception calculator gives:

Probable date of ovulation:  September 15
Possible dates of conception:  September 11 to September 19

Given that this was a very early ultrasound, I cannot see it as being off by more than a day or so.  Certainly not a month or more.