Players can spend a maximum of 20 XP per every 4 weeks on stats or skills. XP is first taken from the character pool, then from the player pool.
The skill caps (the out-of-CG value) limit how far skills can be advanced. Note that if you have an Adept or an Inept, this is calculated on top of the actual skill value, so your final result may be above the cap if you have an Adept or below the cap if you have an Inept.
For skills, the cost is calculated according to this scale. The Asset Fast Learner reduces the cost by 1 point as long as the target is from 10 to 99. The Flaw Slow Learner increases the cost by 1 point as long as the target is from 10 to 99: