Alternator...

--------OK----------forget what I told you earlier. You EVIDENTLY HAVE an import car and THAT IS NOT the "normal" U.S. alternator setup, rather Bosch or something else. Not familiar with the wiring on those from what I can see there........

THAT MAY BE a Delco "one wire" swap which no longer needs an external regulator. DO NOT ground the green. It may be still connected to the regulator. Show us the firewall area or try and locate the regulator

Also IF this is a "one wire" that could explain the somewhat low reading.......this is because a "one wire" alternator SENSES the charging voltage right at the alternator output terminal. This means that voltage drop in the harness (on the path to the battery) will cause the battery to run a bit low