We count 49 days between Pesach and Shavuos, but there are really 50 levels. The 50th level is the one that puts it all together.
There are four chalakim of the Shulchan Aruch, but the “fifth one” represents the seichel of the person who has learned the four chalakim but now has to figure out how to apply it to his life even when it’s not clear-cut. So it’s not really a separate cheilik per se’ – it’s the way of understanding the other four chalakim.