Confused

Ok according to my LMP due date is aug.30th. Bringing me to 11 weeks, 2 days.

My dr today got me st 11 weeks 4 days, just off her circular thing.. and due date is sept.3rd?

That's 4 days difference in due date, but two days difference weeks wise? And she went of my LMP?!?

How does this make sense lol.