After you have been pressing the start- and stop button for a while, the time will eventually come when you want to know just how much time you have registered on the activities. A quick summary is already displayed in the main window and you can see the current totals in the "Project statistics" window. More detailed information can be obtained with the "Generate report" window. This window can be accessed via the menu item "Project \ Generate report...". The functionality of the "Generate report" window is described on its own help page, but this section details the specific settings and choices you have while creating reports.