The first number is how many years' worth of results to include, going back from the current month. All of the current month back then will be included.
Only your top results count. The second number says how many to count.
These rankings are done in a relative way - you get points from the players you beat in a tournament. The third number says how many players. For example, a value of 10 means you get points from the 10 highest-ranked players you beat. You can leave it blank or put 'all' to get points from everyone you beat. This will make larger tournaments affect the rankings more.