I think there have been some inconsistencies from the very beggining.As IvyLeague pointed out,by late S3 Paulie was a captain.But in S2 we see him getting bumped up to underboss.In the episode where Furio is brought over to America,Tony and Paulie are having a meeting and Tony mentions that "from now on it's me,and then you and Sil together,that's the new pecking order".