Well, it seems very unclear for me too.
I will just try this when I confront a Team with a great leader.
My questions are still: ¿Does box makes your rebounds better or worse?
Usually outside boxes are intended to defend very well the best outside player of the other team, and the 4 resting players of your team defend the zone, leaving the outside players of the rival more freedom.
¿Is that what it happens here?