Our little bean measuring at 6 weeks 5 days on 2/20

I have irregular cycles, but my best guess was that I would measure at 8 weeks. The OB said that baby looked healthy, so I'm trying not to worry. According to this ultrasound, I should be 7 weeks 3 days now. Anyway, I was too excited about seeing the little heart beat that I didn't ask what everything was! Is it possible that the circle at the top above the measurement is the head and the crown didn't get measured?