Relative Skill Level
Skill level reflects a combination of talent and training. For instance, a DX 17 warrior has a lot of raw talent. He could quickly learn Shortsword-17, as this is only DX level for him. A DX 10 fighter would need considerably more practice to become that skilled, as Shortsword-17 is DX+7 level for him.
Such details are often unimportant; two warriors with Shortsword-17 are equally good at smiting foes, regardless of whether their skill is due to talent or training. However, there are times when you need (or want) to know the difference.
It is easy to compare talent – just look at the controlling attribute for the skill. In the example above, the DX 17 swordsman is clearly more talented than the DX 10 fighter.
To compare training, you must look at relative skill level. You can calculate it quickly by subtracting controlling attribute from skill level. In our example, the DX 17 warrior has a relative skill level of 0, while the DX 10 fighter has a relative skill level of +7, and is better trained.
Relative skill level becomes important when using the next two rules; therefore, you might opt to note it in parentheses after your skill level; e.g., "Shortsword-17 (+7)."