(Update: the New York Times called it "a generously announced 16,303.")
This photograph from the first quarter shows a good number of seats full in part of the upper bowl--"there was some extra juice in the building," wrote the Record's Al Iannazzone--but many empty seats closer to the floor. Here are a couple of other photos (time taken unclear), plus one from near the game's end.
Then again, with the NBA, official attendance does not refer to gate count but rather all tickets sold or distributed. That bolsters my estimate of a 25% fudge factor.