You can swap, or flip, grading values so they go from a positive value to a negative value, and the other way around. For example, this can be useful when copying grading values from a left sided piece to a right sided piece.
To flip grading settings:
If it is not already open, open the Sizes and Grading pane.
In the 2D window, select the grade point or points whose value or values you want to flip.
In the Sizes and Grading pane, click Flip, then: