Dating ultrasound, confused?

I went to my first ultrasound at what I thought was 7 weeks + 1 day. I measured at 6 weeks and 3 days. My LMP was May 3rd. I left the appointment thinking...okay I’m 6 weeks and 3 days.

Today I saw my GP, and she’s like “you’re 8 weeks + 4 days today”. I said “I’m 7+5 bc measured at 6+3 at my ultrasound.” Then she said, “we won’t change the date because the baby would come either 2 weeks early or 2 weeks later”. So now I’m confused! Am I 8+4 or 7+5 days pregnant?