how to read alternator voltage regarding manufacturer data?

when the car manual said:alternator voltage should be between 13.7v and 14.75v,does the spec refer to the voltage reading between the battery poles(when engine running of course)or between alternator b+ connection and battery negetive pole?because the voltage between the alternator b+ and battery negative pole is higher from between battery poles(because of voltage drop)so what is the correct test that refer to manufacturer data?
best regards
igal