due date has been changed

Colleen
So we had what I thought would be our 19 week 1 day scan today and she says I'm measuring at 17 weeks 5 days. They changed my due date from the 17th to the 27th of January, but everything is growing healthy and right! And they confirmed it is a BOY!! 💙💙💙
Anybody else had they due date changed like this, I'm wondering because I know when I got pregnant and it's not adding up 🤷🏻‍♀️