Yeah, probably would make more sense to include examples like the ones I put here to explain the shapes on the tooltips themselves.
The multis go double -> triple -> quadruple -> 5x -> etc so definitely no quintuple anywhere. But even if it was quad with just one booster, I guess that might have been a bug. But boosters also affect other boosters so you could go booster -> booster -> multi and end up with quad even if it only had on direct neighbouring booster.

