This sample shows how, in Windows 10, if you call Keyboard.IsKeyDown in the Form.Load event, on a 4K screen, the window size will be smaller than it is supposed to (depending on user settings, applications on UHD displays must be scaled, usually at 250%).
Although it's not really a problem at all, in most cases (there are not many reasons to call Keyboard.IsKeyDown anyways), it might reveal some imperfection that would be great to fix, in order to prevent side effects.
You can see a discussion about this issue here.