Schedule+ uses this subkey to track the Appointment books of other Schedule+ users that you had open when you exited Schedule+. The following is the Registry path for this subkey:
HKEY_CURRENT_USER\Software\Microsoft
\Schedule+\Microsoft Schedule+ Appt Books
Count REG_SZ number
Indicates the number of other users' Appointment Books you had open when you exited Schedule+. More entries appear in this subkey when the number is nonzero.