Then don't do that. 😊
Having said that, it's just a regular messagebox, so it doesn't support scrolling. But you can do the usual trick to move it around (even offscreen): press Alt+Space, M, then keyboard up until you can see the buttons, then Enter (it will snap back to the screen and hide the buttons, but now you know what they are), tab to the appropriate off-screen button and enter again. Or press the appropriate hotkey for the buttons (Y/N/Enter/Esc) once you know what they are.