When they said 750 they included full-fledged members. I guess all ~750 are confirmed suspected of having some involvement in the criminal activities of the family, at the least. As for which ones are and aren’t members, I bet even the FBI doesn’t know at all times. The ones you hear about made some splash in the underworld, and in LE circles. Who can say with a 100% certainty which Italian guy in a lower tier position is and isn’t made? Few people are going to come out and say “I am a member of an organized crime family”. Regardless of what surveillance techniques or informants they have.