If you mean how to create it, after making x example a first roughing, right-click on the icon in the tree and choose creates residual material model, expand the tree and you will see it active, then right-click the first roughing and choose to add residual material model, at this point you do with the dx on the active residual model and choose to calculate, making a 2nd roughing position you will have to indicate the residual material to consider