6+2 but measuring a week behind (kind of)

[Irisrises]

I went for a scan and i was expecting to be aound 6+2. The sonographer started the scan by saying the measurment was 6+2 then said 5+2. I asked which one and she said the yolk sack measured 6+2 and embryo was 5+2.
I said so its a miscarriage? She booked a scan in 10 days and avoided answering questions about dating. She said 'we only go off the scan dates'. I was out the room within a minute.
Ive thought about it and if the yolk sack is 6+2 then that is the gestational date. So the embryo stopped growing a week ago?
I've googled this but cant find anything similar. Lots of comments on baby measuring early but not about a later date on yolk sack

Was this a private scan or an NHS one? TV or pelvic? At this stage of pregnancy, its absolutely tiny and mm's. Alot can depend on the scanning equipment being used, the skill of the sonographer and whether TC or pelvic. Also- it can depend when ovulation actually occurred and even when someone has very regular cycles this can vary.

I'm afraid I can't provide any specific advice but wishing you all the best x

It was an nhs internal scan