euhm, i can explain the entry ranking...
It consist the best 18 result of the last 52 weeks and they make a difference between mandatory events(grand slams and master series) and non mandatory events(smaller tournaments) max 5 , master cup is 19th tournament.
For example a player in top 50 who didn't play Roland Garros would get a zero,a player outside for example outside top 200 wouldn't-- not mandatory for him
For more information about how much entry ranking points you can earn i a specific tournamet look at www.stevegtennis.com
entry ranking points or for a breakdown www.tennisfacts.com