Based on the formation definition in those pictures I would say only 1 Broadside. Also only 1 Ghostkeel. As the formation doesn't include the word unit when referring to the Broadside or the Ghostkeel. It does include the word team/unit when referring to Pathfinders/Stealth suits.
I would agree with TauMinded. This is the same kind of wording in the Canoptek harvest formation with the Tomb Spyder. Since the formation sheet only lists one of a given model, in this case the Ghostkeel and the Broadside, then they will be just the one model. The stealth team on the other hand could be a made to be a full 6 member team since it lists them as a unit.
Definitely only one Broadside. It doesn't say "1 Broadside unit" but "1 Broadside". It's pretty much intended by GW to write things like this by now considering Skitarii have the very same problem with some of their formations with their chicken walker.