I agree, but I also don't see how they could have had anything less, considering they were the strongest of the Five Families. In the novel Clemenza also states that they outnumber the other four families and that they could muster a thousand men; I think that was their entire criminal work force including associates. Also bear in mind that even in times of war, there still need to be men left to look after the rackets. So Sonny's statement probably didn't include the entire family.