Wrote that while in the waiting room for an appointment I'm just getting out of now, it's because I'm having twins, apparently. They can't tell the sex, just that twins are there.
We spend the first 2 weeks of our 40 week pregnancy, not actually being pregnant at all. Think about it. They count the 40 weeks starting from the first day of the last period. You don't fall pregnant till about 2 weeks after that so a baby born at 40 weeks pregnancy is only about 38 weeks old and only 38 weeks since conception.
I wonder if that accounts for your discrepancy of 9 vs 7 weeks.