These options are displayed by clicking the Curly corner button in an operation's milling tab.
Check the Enable curly corner toolpath checkbox to enable this toolpath technique.
The corner radius is the radius of the circular toolpaths (or trochoids) that are inserted. The corner radius must be greater than or equal to the Stepover.
The minimum angle is the threshold for inserting the trochoids. If the angle between two toolpath moves is less than this angle, no circular paths will be inserted between the moves.
The Stepover is the same as the Distance between cuts. It is presented in this dialog box so that it can be viewed along with other relevant parameters.