This window appears during Add operation. Select a new operation number for the new operation. If the part already contains operation numbers such as 10, 20 and 30, then a number like 15 or 25 should be selected, if the operation should lie between these numbers. There is a safety feature that will not allow you to save a new operation on an existing operation. If you enter an existing operation, a warning text will appear at the bottom of the window in red font, telling you that the operation number already exists. To view all the existing operations for the selected part to which you want to add an operation, click the Existing operations button.