艮 is the indexing radical and carries the body of the original sieve graph. The combination once depicted clean grain falling from the sieve - the goodness of pure, sifted grain - which is how 良 came to mean fine, excellent, of good quality.
The top dot is an abstract marker - historically the topmost grain rising out of a sieve in the original graph that depicted grain-cleaning. In the modern shape it has hardened into a positional indicator pointing at the body of the char.
