Algorithmic, or manually set?
Predominantly algorithmic, as
D*star has explained but with some manual intervention in special cases.
Those interested might like to take a look by left-clicking on
MEMBERS in the menu bar, above. Now left-click on the
Position column heading and the page will be sorted into alphabetical order on members'
Position. Scroll down and left-click on
Page 2. You will eventually see many who have
Just arrived. Now left-click again on the
Position column heading and the page will be sorted into reverse alphabetical order on members'
Position.