The add values button on the symbology tab in layer properties adds only values already existing in your database. People have to constantly add new values to their existing symbology as new value combinations get entered. This impacts people who have published map services especailly, constantly having to republish service when ever a new combination of values get entered. The new button "Add All Possible Values" would add all permutations of your value fields allowing the user to set symbology for all combinations, even those that do not exist yet. Thanks.