Was that via an ultrasound or fundal measurement? Via ultrasound is the size of the baby. For example, my son was measuring 13 days ahead as of 2.5 weeks ago (I was 29+6, I'm 32+3 now). This puts him in the 74th percentile, and if he starts in the same percentile he'd be about 8.5 lbs at 40 weeks. My doctor told me that the fundal measurement, as long as it's within 1-2 cm of the week, they don't worry about it. So overall, I wouldn't be too concerned about measuring one week ahead at this point in your pregnancy.
but at my ultrasound my due date was suppose to be November 24 n ultrasound put it to the 18