The station may need to write to a property like Out Of Service or Notify Type. If an exported NumericWritable has an alarm extension, and you want to permit external BACnet writes to its alarm limit
values. In both cases you need to configure the BACnet user to have admin write permissions on the exported Boolean Writable and NumericWritable points.
The BACnet user is initially created without any permissions. This procedure documents how to assign the necessary permissions to the BACnet user.
BACnet Writable at priority. 
Permissions property.BACnet user permissions also apply to writes of any exported files and histories. While a password for the BACnet user is technically not needed (for external BACnet access), you should assign one anyway, because of the write permissions typically assigned.