Site Leaderboards are based on a 6 month sliding window of tournaments. The total number of points a player has acquired in that window is divided by the number of tournaments they have participated in in order to achieve an average. This is the number that is used when decided the rank in the sitewide leaderboards.
Further, the fewest number of tournaments that a player can participate in when calculating the average is 6. Therefor if a player has played in fewer than 6 tournaments their total number of points is still divided by 6. Currently there is no upper limit.
The amount of tournament points received from an individual tournament is also based on how long ago that tournament was played, thus it decreases over time gradually in the 6 months that it is considered when calculating tournament points.
I suggest a player’s top 6 scores be taken, instead of all of them. This way a few bad results can be left out of a player’s calculation if you play in more tournaments.