Dating scan today

Brooke 🎀

I had my first dating scan today. The first day of my last period was 7th April. I fell pregnant the next month. I thought i was 7 weeks and 5 days today. I went for my dating scan and it said i was measuring at 6 weeks and 2 days?? I am very confused?? As this happened to anyone? I saw the heart beat and it was all good she said. Was normal and healthy.