A progress box is displayed. If the model in which you are reverse engineering already contains data, the Merge Models dialog box is displayed.
For more information on merging models, see Core Features Guide > Modeling with PowerDesigner > Comparing and Merging Models.
The classes are added to your model. They are visible in the diagram and in the Browser, and are also listed in the Reverse tab of the Output window, located in the lower part of the main window.