HP EliteBook 840 G3 - Manual (Page 41)

Component Description
Each key on the keypad performs the function indicated by the icon in
the upper-right corner of the key.
(7) num lock key Turns the embedded numeric keypad on and off when pressed in
combination with the fn key.
NOTE: The keypad function that is active when the computer is
turned off is reinstated when the computer is turned back on.
Using the keyboard 31