Torg uses charts to determine results of dice rolls.

The easiest way to autocalculate the results in roll20 is with the powercards script.

See this thread on the forums

!power {{
--txcolor|#FFFFFF 
--bgcolor|#7A007A
--name|Manual Entry Chart
--Roll Total:| [[ [$R] ?{Value|0} + 0d0 ]]
--?? $R == 1 ?? Bonus:| -10
--?? $R == 2 ?? Bonus:| -8
--?? $R == 3 ?? Bonus:| -6
--?? $R == 4 ?? Bonus:| -6
--?? $R == 5 ?? Bonus:| -4
--?? $R == 6 ?? Bonus:| -4
--?? $R == 7 ?? Bonus:| -2
--?? $R == 8 ?? Bonus:| -2
--?? $R == 9 ?? Bonus:| -1
--?? $R == 10 ?? Bonus:| -1
--?? $R == 11 ?? Bonus:| 0
--?? $R == 12 ?? Bonus:| 0
--?? $R == 13 ?? Bonus:| 1
--?? $R == 14 ?? Bonus:| 1
--?? $R == 15 ?? Bonus:| 2
--?? $R == 16 ?? Bonus:| 3
--?? $R == 17 ?? Bonus:| 4
--?? $R == 18 ?? Bonus:| 5
--?? $R == 19 ?? Bonus:| 6
--?? $R == 20 ?? Bonus:| 7
--?? 21 <= $R AND $R <= 25 ?? Bonus:| 8
--?? 26 <= $R AND $R <= 30 ?? Bonus:| 9
--?? 31 <= $R AND $R <= 35 ?? Bonus:| 10
--?? 36 <= $R AND $R <= 40 ?? Bonus:| 11
--?? 41 <= $R AND $R <= 45 ?? Bonus:| 12
--?? 46 <= $R AND $R <= 50 ?? Bonus:| 13
--?? 51 <= $R AND $R <= 55 ?? Bonus:| 14
--?? 56 <= $R AND $R <= 60 ?? Bonus:| 15
--?? 61 <= $R AND $R <= 65 ?? Bonus:| 16
--?? 66 <= $R AND $R <= 70 ?? Bonus:| 17
--?? 71 <= $R AND $R <= 75 ?? Bonus:| 18
--?? 76 <= $R AND $R <= 80 ?? Bonus:| 19
}}