lol, and the clouds part in the heavens as the angels sing and fire sheds some light on the subject.....lol
okay here is what I think (hoping it's correct) the answer is that you are looking for....
Pitt has a different designation for some student groups. Panhel and IFC are governance groups, which over see the member groups operations. It lets us have more money from the student activity fee. Other organizations also have this status; the Black Action society and most recently the Asian Student Association. By being a member of the governance group we take care of our own affairs to an extent. Individually organizations under the groups can't use our student organization resource center (fax, mail, copies, etc.) Panhel and IFC also have their own office, where some groups only have a cubicle in the union.
NPHC, however, does not constitute a large part of student population and therefore are a student organization. All student organizations are required to have 10 members and a constitution and be registered with the SORC. That's where the 10 persons comes from.