I have the same - scan is on Tuesday because their dating is just based on first day of last period, which would put me at 12 weeks that day, but I know my cycle was 37 days (it was longer but regular!) so the nhs calculator puts me at 10+4 for that day.
Crazy that the system the trust uses for self referral doesn’t just use the nhs calculator…
theoretically the dating/nuchal scan can be done any time between 10 and 14 weeks according to the nhs website so hopefully will be fine 🤷♀️ If they make me come back I might as well set up a camp bed, I’m in and out so much now they’ve decided I need to be on levothyroxine while pregnant 😂