How Skills Look and Work
First you have your base skill level from 1 to 100
Then you have a certain number of Variance Dice: either zero, or 1-6d10.
Then you have a Luck number for each skill between 1 and 6. For each Variance Die you roll, also roll 1d6. If you roll your Luck number or higher, the result of that Variance Die is added to your Base Skill for the task. If you roll lower than your Luck number, that Variance Die is subtracted from your Base Skill. The Luck number for any given skill is almost always 4 (i.e. 1,2,3 bad, 4,5,6 good, a 50/50 chance for good or bad variance), but some game features may alter this number.
Your final skill configurations look like so:
Aiming: 50 (2d10, 4+)
Specializations: It is possible to be particularly skilled in a certain, more narrow range of activities described by that skill. For instance, most skilled Athletes specialize in a specific sport, a Pilot could specialize in different categories of spaceship, and thugs and outlaws everywhere have specialized in Aiming all sorts of weapons. Specializing in a skill costs 3 XP. When making skill tests related to one’s specialization, that character’s effective Base Skill is considered 5 points higher, and the Luck value for the character’s Variance Dice is decreased by 1 (making it more likely that the Variance Dice will be helpful). In addition, if and only if a character is attempting a skill test in his specialization he may choose to add or subtract 1 from the number of Variance Dice rolled.
Given sufficient XP, a character can buy any number of specializations for any given skill, although Gamemasters should use their judgment to prevent ridiculousness.
“Won’t I have to roll a lot of dice?”
Yes, for a skill with maximum variance you would have to roll 6d10 and roll a d6 connected to each of those d10s, and then add and subtract those six numbers together and finally add or subtract that total from your Base Skill. And all those variance dice might even out to only a negligible bump up or down, or they might average out to no variance at all. Most of the time, if you’re rolling a large number of variance dice, doing all the math is probably not necessary- a quick visual inspection of the Luck dice should help determine if there was a significant “swing” either way or whether it mostly evened out. Often, small amounts of variance are negligible and a precise final total is not needed, only an estimate as to the nearest increment of 10 the result is in (rounded down).
Ultimately, if you as a player don’t enjoy rolling lots of dice and doing the math, choose skills with low starting variance and/or lower the variance of your skills with skill points.