How to get the dialog?
Menu Bar: View → Edge Brushes
Keyboard: F3
Dialog options
An image of the dialog is shown to the right (click it to zoom).
Brush ID
This is the identification number of the brush that you are editing.
Brush Size
This allows you to choose what size of brush to paint with. The small brush is 2 by 2 tiles in size, and the large brush is 3 by 3 tiles in size.
Heights
This allows you to choose a height for the brush. When this option is switched on, the height you have chosen (either that shown by the slider bar or sea level) will be pasted into the height map wherever the brush is pasted. Using this option you can quickly create areas of raised ground or water.