What are registry values ProfileUnloadTimeHigh and ProfileUnloadTimeLow for?

I have noticed that HKLM\Software\Microsoft\Windows NT\CurrentVersion
\ProfileList\<SID>\ key contains DWORD values for
ProfileUnloadTimeHigh and ProfileUnloadTimeLow.

What are these values for?

Does these values signify when user's profile was last unloaded? Or
when the user's roaming profile was last syncd with central server?

Microsfot Experts please reply this if you know.

Brijesh Mishra