Alternator output should rise to 15.0v after starting. This should only happen after the battery is recharged, so on a flat battery it may be some time.
After the alternator has hit the 15.0V mark, it should drop to 13.6 - 14.0v.

The battery voltage should be at 13.6 - 14.0 v at idle, with no accessories or lights on. Even with these on, the battery voltage should be at 13.6 - 14.0 with the engine doing >1K RPM.