The chart is helpful, but keep in mind it's a GFII prop. There's no way I'll believe that Fredo was underboss and that Tom ever regained his position as full-fledged Consigliori. In the novel it says that Vito was considering making Sonny his underboss. Apparently, that never happened nor was there ever a mention of an alternative to Sonny. But, it's only a novel; it's only a film.