Number of Loops of the DT Chart is a top list that counts the number of loops users have made on the D/T grid. The secondary sort is done on the profile name, not on the date when the loop was succeeded. Each geocache is only counted once per profile, even if it has been logged a multiple number of times.
The data is updated every hour for users with at least 5 loops (5*81 DT), every sixth hour for those with at least 1 full loop (81 DT), daily for those with at least 49/81 and weekly for the rest. Note that the data is still updated based on the data that Project-GC have locally, see Data synchronization for more information.