Baby measuring behind.

Today I had an ultrasound to check on my SCH. She asked me if I was given an official due date yet and I said no, but the ultrasound I had the week before the baby was measuring on time. So I assumed my due date remained the same. So during the ultrasound she said the baby looks fine but is measuring two days behind, bumping my due date to 8/31 instead of 8/29. She said it’s normal. But I wanted to know if people have had the same experience. I’ve never had this issue in previous pregnancies. Everyone always measured on time or a day ahead. Should I change my due date in my app? Could the baby end up measuring on time in the future? Any insight would be appreciated.