If I were told what you were I would be thinking that I was further along - due sooner. But I had only about 5 days between the dates I was given and was told by a GP and OB and m/W on separate occasions that the earlier scan is usually the more acurate for dates.
...in my case they have just gone with the average of my cycles and given me the later date to help give me more time to achieve a vbac.

Congrates on your pregnancy.