The first ultrasound showed a gestational age of 2 weeks longer than t…

The first ultrasound showed a gestational age of 2 weeks longer than the gynecological one. The second ultrasound showed a gestational age 1 week shorter. Therefore, the gestational age was 11 and 5 according to the ultrasound, while on the second ultrasound it was 12 and 1. The size of the belly was 14 and 4. What does this mean? Is this normal? Or is it just because the baby is small?