Came from this comment.
Things are very simple at the moment but there's room to tighten things up more and make it clearer.
Once #74 lands then these ranges are documented here. Currently the table has just "From" and "Title" columns. Work on this issue will add a "To" column, which will need to include research to identify what those to values should be for each range. The tighter the better (they can always be opened out later to add more codes if needed, assuming nothing adjacent).