they determine from the CRL when doing the ultrasound scan. I've seen people's EDD got adjusted between 5 to 7 days after a few ultrasound scans along the way. as long as gynae says fetus is growing, I think all is well. don't worry too much.
Don’t worry too much about that, it fluctuates somehow as it’s afterall an estimate. As long as baby is showing a good growth progress you are on the right track 😊