get-MailboxFolderPermission double folder?

Hi,

during trying of configuration permissions for Calendar on Office 365 (maybe on Exchange 2013 will be same), i found some strange:

PS C:\> get-MailboxFolderPermission -Identity "office\calendar"

FolderName           User                 AccessRights
----------           ----                 ------------
Top of Informatio... Standard             {None}
Top of Informatio... Anonym               {None}

and another folder:

PS C:\> get-MailboxFolderPermission -Identity "office:\calendar"

FolderName           User                 AccessRights
----------           ----                 ------------
Calendar             Standard             {AvailabilityOnly}
Calendar             Anonym               {None}
Calendar             user1                 {PublishingAuthor}
Calendar             user2                 {PublishingAuthor}
Calendar             user3                 {PublishingAuthor}
Calendar             group1               {PublishingAuthor}

the difference in office:\calendar or office\calendar without colon. These settings are for one mailbox, but why it has TWO different Calendar folders with different permissions?