To edit the plane to board edge clearance, you would need to edit:
The Pullback Distance found within the Layer Stack Manager.
1. Design ► Layer Stack Manager. 2. Select the Plane layer in the stack-up 3. Open the Properties panel 4. Edit the Pullback distance within the Properties panel
Alternatively, the Pullback Distance can also be edited directly within the table (this is the method used for older versions of Altium Designer). To do this:
1. Right-click a Column Header ► Columns
2. Within the list, enable the Pullback Distance Column for view
3. The column should now appear on the table, select the Plane layer and edit the column entry.