Game Guide | ISRO Classic
There's a context between the collecting of EXP and SXP.
It can be described by the level gap.
The level-gap explains the numerical difference between the highest masterylevel of a skillcategory (it doesn't matter if it's a weapon- or a force-skill) and the current character-lvl.
Current char-level: 20
Masterylvl (Cold Force Mastery): 15
Masterylvl (Fire Force Mastery): 10
Masterylvl (Heuskal): 19
The level-gap would be 1 in this case, because Heuskal's highest Masterylvl is 19 and the current character-lvl is 20.
The highest level-gap you should have is 9,
because everything beyond it wouldn't have any influence on SP/EXP.
The level-gap is an important part of farming of SP, A good SP-farming-technique is the most important part of a good build. In short: The higher your level-gap, the more SXP you earn. But in return: The SXP-Bonus is antiproportional to EXP.