This is a bug in S Health that the S Health team promised to be fixed way back in S Health v4.6, but didn’t.
We got the following guide on how to resolve this S Health issue from the Samsung S Health team:
In order to resolve this issue, user can try either one of following:
1) Clear S Health data from Android Settings > Applications > S Health > Clear data.
2) Change the locale of the phone and wait 1 day.