Files in Data/ folder:

Folders.xml - XML file containing folders info for users and groups. Can be edited at Notepad or at admin panel (AdminPanel.aspx online tool). 
By default user Administrator, Domain Users and Domain Admins groups has access to /DemoFolder/Folder1 and /DemoFolder/Folder2 folders.

Errors.xml - XML file containing errors occured at application. See "Troubleshooting" section at Documentation.
Logs.xml - logs