You got something wrong. Or I did =]
There are two "qualities": percentage (relative) and overall (absolute). Like, 104% (41) -- 104% is relative quality, 41 is overall quality. Every point in OQ equals 4%, always.
To get a star you need 20% or 5 OQ, or 20% * 15 = 300% to skills (attributes).
The pace of gaining XP is unique for every player. It depends on amount of stars this player has, his age, and a hidden parameter. There is more, but it's a different story.
Read this if you are interested:
https://forum.topeleven.com/tutorial...tml#post500463
https://forum.topeleven.com/tutorial...ng-system.html