Some ASUS laptops come with a numpad (numeric keypad) embedded in the touchpad. You can toggle between the touchpad and numpad using a button placed in the top right-hand side corner of the touchpad. That is, after you follow the instructions below, because this feature is not available by default on Linux.

Source: LXer – How To Get The Numpad Embedded Into The Touchpad Of Some ASUS Laptops To Work On Linux