I received a notification that a particular file was transitioned by someone and "...has reached the end of the revision list."

I remember getting this once before a few years ago and I found how to change it.  It was an alpha list and you had to type into it what characters could be used.  After listing A-Z (skipping a few) you could put down AA-AZ and then BA-BZ, etc., listing each individually.  I remember increasing it a bit but apparently not enough for some of the more popular files with lots of configurations that get changed often.

Does anyone know where this is located at?  I looked all over the admin page.  It is mentioned four times in the admin guide but not one tells you where it is.

Thanks;

Stephen