The properties editor allows you set any of the properties of the selected objects using individual controls specific to each of the objects parameters.
Pcb Arc Cutout Properties Editor
To see what each of the editor's controls does: move the mouse cursor over the control in DEX (not this help topic) and a popup tooltip will appear.  A Typical Popup Tooltip for a Control Can't See the Tooltips? If you cannot see the tooltip: make sure the Show Tooltips check button on the left of the DEX status bar is 'checked'.  The Show Tooltips Check Button |