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 }}