Using CustomBrush_Landmass Brush creates an inverted pyramid on the landscape

When using the CustomBrush_Landmass Brush, clicking the landscape should add a pyramid shape landmass but instead creates a inverted landmass.

Regression tested on //UE4/Release-4.27 @ 18319896

Repro Rate: 4/4

1. Create or open any project
2. Enable LandMass plugin
3. Create an empty level
4. Change to landscape mode.
5. Enable edit layers then create the Landscape
6. In the Sculpt tab select Blueprint
7. Set blueprint brush for CustomBrush_Landmass
8. Click on the landscape in the viewport

Expected Results: A pyramid rises up out of the landscape

Actual Results: The pyramid is inverted going into the landscape