It's because the window only paints itself once unless there's reason to repaint it again. For example, the number should increase if you hide the window (maybe minimize it), then reshow the window. It will have repainted a number of times. FYI, you can force a paint in code using the Invalidate() method of the Form class. Invalidate tells the operating system that a repaint is needed, and it will repaint at the next opportunity.
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