The new Ranking menu item shows a TT365 computed national ranking for each player linked with the SHAW league.
TT365 calculate the rankings by starting with National Rankings for the players that have them and then computing a ranking for everyone else based on actual wins and losses, taking into account the ranking of the player beaten or lost to (across all leagues not just Shaw).
The accuracy of this should naturally self improve over time.
More explanation is shown on the Ranking page itself and via a link from there.
If a player shows on the list that you would not expect to, it will be because they were registered for a SHAW team at some time in the past and have never been un-linked from the SHAW league. (If you look at your own profile on TT365 - Profile icon top right then Membership/Profile/My leagues and clubs - you will see the leagues that you are linked with.)
Please note that these rankings have not been used for the calculation by Frank of the Harvey Shield ratings (and so will also not be used for the SHAW closed handicap event). This may change in future if the rankings look reasonable for all players.