I see this number for one of the sessions but not sure what it is indicating.
That is the number of unread markup alert notifications.
https://support.bluebeam.com/online-help/revu21/Content/RevuHelp/Menus/Window/Panels/Studio/Studio-How-To--MV.htm#Alert_Other_Session_Attendees_to_a_Markup
Will it be possible that this notification number alert be on the "Notifications" tab as well after the user click on the session? For most new users can't easily find where the notifications are after they got into the session.