A Windows system tray balloon is used to notify the user of events when the Attendant is hidden. If the balloon notification ...

"A Windows system tray balloon is used to notify the user of events when the Attendant is hidden. If the balloon notification is disabled by policy, then a warning is displayed in Attendant indicating that the user won't be notified via a balloon as a result. This policy prevents that warning from being shown to the user.  If this policy is set and non-zero, the warning is not shown.  If this policy is not set or set but zero, then the warning is displayed to the user."