the corresponding number on the numberpad—not on the keyboard above the letters ('Num Lock' usually needs to be enabled)
NUM+ and NUM−
the corresponding key on the numberpad
Note for Windows 2000/XP users: do not press right Shift five times in a row as it turns on the Windows Sticky Keys. Doing so will mess up the ability for your keyboard to recognize commands. If the box for sticky keys appears, press cancel. If you don't need the accessibility features, you can disable sticky keys: go to Start → Settings → Control Panel; select Accessibility Options, and for each of the options, StickyKeys, FilterKeys, and ToggleKeys, (1) clear the "Use …" checkbox, and (2) press the "Settings…" button and clear the "Use Shortcut" checkbox.