Polycom WEBCOMMANDER 8 - Manual (Page 147)

MGC WebCommander User’s Guide
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The End Time window opens.
2. Set the new time the conference should end using a 24-hour format;
select the new hour and minutes. You can end the conference before its
predefined time, or you can extend it. The maximum conference duration
allowed is 99 hours and 59 minutes. If you try to select a a duration that
exceeds 100 hours you get an error message.