The players pretty much ignore the Race rankings until it gets near the Masters Cup at the end of the Season.
The Entry rankings are for the previous 52 weeks, so someone like Tim, who got to the semis of the US Open last year, will drop several places if he contiunues his abysmal run as he has loads of points to defend. Conversly, Rusedski only needs a couple of wins to leap into the top 20.
Challengers and Quallies dont count towards the Race, as it's purely based on ATP main events as shown HERE
but Challengers do count towards Entry rankings. Hence Andy's stellar progress this summer.