SYSINFO.nOSMinor not working for Windows 2012 R2 and Windows 8.1

For InstallScript projects, does anyone know why InstallShield 2012 returns 6.2 in the SYSINFO values for Windows 8.1 and Windows 2012 R2 which should be returning 6.3? Specifically in the SYSINFO.nOSMajor and SYSINFO.nOSMinor versions.

I don't mind not having specific constants for them because I'm using an older version of InstallShield, but I would still expect the versions returned to work.

Any workarounds as I have to detect these OSs in my installation!