In order to find the count of all the respective Calendar items for all users, please run the below query against the Archive Manager dataabase
select mailbox.MailboxID, mailbox.name, folder.folderID, folder.name as FolderName, count(messagefolder.messageID) as TotalFolderItems from mailbox, folder, MailBoxMessage, MessageFolder where mailbox.MailBoxID=folder.MailBoxID and mailboxmessage.mailboxid=folder.mailboxid and mailboxmessage.messageid=messagefolder.MessageID and messagefolder.folderid=folder.folderid and folder.name='Calendar' and messagefolder.messageID=mailboxmessage.messageID group by mailbox.MailBoxID, mailbox.name, folder.FolderID, folder.name order by mailboxID
