Is 4mm CRL with a heartbeat normal at 5+6?

[measurem]

This was the measurement they gave me at the scan, and they saw the heartbeat. This was at 5+6, or 6 weeks. Can’t be sure of dates. They said 4mm is normal but the NHS website says 6mm.

Does it sound ok?

You’re only just 6 weeks so yes 4mm is completely normal they would have said if they were concerned.

baby is tiny and exact measurements are difficult this early on.