Somehow your database contains two "System.Statistics" objects, while only one should exist. This object keeps track of the maximum number of users and the known runtime instances.
Unless you're running multiple runtime instances or manipulate the database manually I would not expect this kind of behaviour.
To solve this you should delete the "System.Statistics" object which has no association with a "System.XASInstance" object. Or simply delete all "System.Statistics" objects as a new one will automatically be created if no such object exists.