Unable to SetFieldFLOAT32Value to 1.5f

I'm using Garmin FitSDK, if this is the wrong forum, please let me know.

RecordMesg A:

A.SetAltitude(1.5f);

auto altitude = A.GetAltitude(); // altitude == 1.6f

This magnitude of this error seems well beyond my expectations.  GetEnhancedAltitude() seems to have the same issue.