Bases on my lmp im 8 weeks. but gestational age was 9 weeks. why? did i ovulate sooner?

LMP & ovulation: Ovulation can occur anywhere from 14 days to 21 days after the LMP dependent upon the length of your menstrual cycle. When pregnancies are computed we use the LMP as an ESTIMATE to standardize the pregnancy length which is accurate to only Plus or minus 10 to 14 days. In other words, trying to backdate ovulation after pregnancy is difficult and is only a "guesstimate".