Elevation fire modifier

[LarkinVB]

The Campaign Gettysburg rules state about fire target modifiers:

The target unit receives a defensive benefit when it is at a higher elevation
than the firing unit. This benefit is normal for a single elevation change and
is doubled for any elevation change of 2 increments or more. The actual
value of this benefit can be found in the Parameter Data .

The Paramater Data is listed as -20% for elevation. Does that really mean an elevation difference of >=2 is a -40% modifier, same as a forest?