The “Allowed Values” filter is slightly misleading and would be more helpful done a little differently. If you tick just one value in the list then only that value is allowed, however, if you tick none and all are unticked then all are allowed – not entirely logical. 

It seems to work on the principle that you’re only interested in allowing certain values, typically this would be a limited number. We’re in the opposite situation of only wanting to disallow a small number and allow anything that is not specifically disallowed. For us this would imply checking 3-4 values as opposed to 50-60. Moreover, with the way the system currently works, whenever you create a new dimension value, that value is not automatically added to the list of allowed values. For us, a disallowed value is the exception, and an allowed value is the rule meaning that almost every time we add a new value we must go through every account and reapply dimension posting limitations. I think that ideally this would involve an option somewhere on what you want the default to be for any new values, ie. allowed or disallowed, but for our purposes just having disallowed would serve 99% of situations.