In a two-layer design, the Reveal is the portion of the bottom matboard showing under the top mat in the Design Editor and Visualize.
The standard Reveal between the top and the next mat is 1/4".
Group Selection of Objects Number of Layers: Properties Tab
Layer Properties: Nesting
Layers: Array Tab
Layers in Set Bevels Tab
Layers: Order Cuts Trace
Layers: Single Tab
Number of Layers: Array Tab
Number of Layers: Single Tab
Template Layers Listing: Properties Tab
Template Layer Reveal: Properties Tab
Template Number of Layers: Properties Tab
Reveals: Application Default Setting