Thank you for your question.
If your ultrasound date differs from your menstrual date by more than seven days at 12 weeks gestation we consider the ultrasound date as more accurate. So if these criteria are fulfilled in your case the date is preponed. You can deliver up to 15 days prior to the due date mentioned provided everything is going well with your pregnancy till then. Please speak with your obstetrician who can explain it better from your ultrasound charts. This will help you feel better about the accurate date and allow you to plan for the delivery and feel in control.
Hope this helps