This option controls the characters that the numeric keypad keys transmit.
In general, you should keep this set to Numeric.
If the number or PF keys aren't working properly, it may mean that this option was incorrectly left set to Application when a host program terminated abnormally. If changing this setting back to Numeric doesn't fix the numeric keypad, check the VT operating level Mode and make sure it matches that of the host. The VT52 setting, for instance, sends different keypad codes than the other (ANSI) modes.
This setting reflects the current terminal state of VT Numeric Keypad Mode, which can be changed by the host. The associated default setting, saved with the model, is VT Keypad Mode Default.