From the introduction:
This Tabletop game uses a D100 dice system. This dice system is called 100DOS, or “Degrees of Success.” When using this system, the users need at least two ten-sided dice.
Some weapons in this system call for a “dice pool.” Dice pools are where a surplus of dice will be needed to determine copious amounts of damage. These can be handled by rolling one at a time, or grabbing a lot of D10s at once, and rolling them all.
100DOS uses two distinct types of dice rolls, the “D10” and the Percentile roll. It is important to note that when the rules say roll 2D10, this is not the same as rolling a percentage roll. When rolling 1D10, 2D10, and so on, you simply add the results of each die. Meaning when you are told to roll 1D10, you roll a single Ten-Sided die, and when told to roll 2D10, you roll two Ten-Sided die.
A 100-sided die cannot be used in the system; rolls are either d% or 2d10; it is important to be able to distinguish the 10s die from the 1s die.