Hello,
as stated in the doc here :
http://managames.com/tennis/doc/Tennis_ ... ml#ranking
The total of points for the entry ranking is the sum of the best 18 played tournaments, within the past 52 weeks, including necessarily the 13 major tournaments to which the player had to participate if his ranking allowed him to enter the final draw
The total of points for the Race is the sum of the best 18 played tournaments, since the beginning of the year, including necessarily the major tournaments to which the player had to participate if his ranking allowed him to enter the final draw
The 13 major tournaments are the 4 Grand Slams, added to the 9 Masters Series
On the 2nd year, when you play a tournament you already played the year before, you'll lose the points from the past year at the end of the tournament, and get the new points from your current year result.