Trying to think of how to put this...

Charisma is a mixture of:

Physical beauty and desirability (self explanatory)
A desirable personality ("desirable" referring to relationships and attraction, specifically)
Force of personality (stage presence, leadership, persuasion)
Performance talent? (this one is iffy; people LOVE a singer or an actor, but this might be considered force of personality)


Example: A comedian with a great personality who is beloved by thousands for his sense of humor, but is not very physically attractive (maybe even as part of his look) would have a high but not super-high charisma (as in, 16 or so).

Or, a gorgeous girl who was vapid and lifeless personality-wise would have perhaps an above-average charisma, maybe 12 to 14.

Just my interpretation, I don't know what was intended by the original rules.