Number of Versions of an Area Instance 
This property specifies the maximum number of versions of an area instance. Possible values are:
No limit
No restriction.
Maximum ...
Restriction up to the number you specify. If you want to specify a number, the fixed area property area instance versioning must have been activated. If the maximum number of area instance versions during operation is less than the current number of area instance versions, no versions can be deleted although new versions can be created once the number is below the maximum number permitted.