THE ULTIMATE GUIDE TO DICE

When an quantity is to be subtracted, the notation is nds-c or nDs-c; so 3d6-four instructs the participant to subtract 4 from the result of rolling 3d6. If the results of a modified dice roll is destructive, it is often taken for being zero or a single; for instance, in the event the dice roll establishes the quantity of harm to a creature.[41][fo