Future Retro Zillion Owner Manual - Manual (Page 6)

CONTROLS AND NAVIGATION
The Zillion provides four soft keys under the display, increment (+) and
decrement (-) keys, and circular touch pad.
Soft Keys
The four soft keys allow you to select functions and variables shown in
the lower half of the display respectively above each key. Pressing one
of these keys will select the function or variable displayed. Holding one of
these keys allows you to make adjustments to the value, and changes
will not take affect until you release the key.
+/- Increment / Decrement Keys
When a function is selected you can use the +/- keys to increment or
decrement the value. Pressing the +/- keys will advance the value in
single steps. Holding down the +/- keys will allow the value to advance
continuously and will increase in speed the longer they are held.