Last day of period doesn’t match up with scan dates

I had forgotten at the time I saw my gp when my last period was so they just gave me a scan to determine due date.

When I had my dating scan, they gave me a due date of September 11 2022.

I have now got access to my old period app and found out last period was November 24th.. According to last day of period my due date is 31st August.

Which is more accurate ?

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