WGT players have a stroke average. A stroke average is not the same as a handicap.
http://golf.about.com/cs/handicapping/a/howcalculated.htm
WGT calculates your stroke average based on the ranked rounds you play as a Tour Pro.
Your stroke average will go up if you have a score higher than your current stroke average.
But only until you have 25 ranked rounds at the Tour Pro tier.
At that point your scoring average is 'saturated' and your scoring average can no longer go up,
Once your scoring average is saturated, if you shoot a score higher than your current scoring average your scoring average will not change. Your scoring average will only change if you shoot a score equal to or lower than your current stroke average.
As you go up in tier the number of ranked rounds required to saturate your scoring average and qualify you for moving up a tier increases with each tier.
At the Legend tier 500 ranked rounds are required to saturate your scoring average.