A sum from 4 to 6 is the only band with no restriction. You can lean on what you already know how to do and on what comes by itself, and you can just as well take up a field you previously had no notion of.
The system treats this as the most convenient position: changing profession later in life is not penalised here, and what has been accumulated is not devalued. The other side of it is the absence of a hint. Where the neighbouring bands are given a firm instruction about where to go, here the choice is left entirely to the person.
That is also where the main risk comes from — spreading yourself thin. The freedom to take on anything turns easily into a habit of finishing nothing.