This is slightly incorrect, it's more how Facebook ranks for searching. Those numbers are for search bar ranking of objects (users,groups,etc) you recently and/or most interact with. You can check yourself by typing the first letter of any of those names and that name is probably the first selection in your Facebook search bar.

A better ranking would be to look at communication_rank and observation_rank in FQL (https://developers.facebook.com/docs/technical-guides/fql/)

SELECT uid2, communication_rank, observation_rank FROM friend WHERE uid1=me() ORDER BY communication_rank