Confused about ultrasound

Just had a second ultrasound, at first she said the sac hadn’t grown and it wasn’t viable, but then she did an internal and said she could see a fetal pole and a heartbeat then she checked the report from the last scan and said the baby had grown as it should.

I’m just confused last week I swear the tech told me I was 5+5( which was too early for my dates anyway) but when today’s tech read the report she’d recorded me as 4+6 and now a week later I’m measuring 6 weeks.

Just looking for some reassurance o guess, has anyone had anything like this before? Xx