Octave shifting on PX-320

[anotherscott]

To change the octave of your left hand sound (when using a split), the instructions say, "While holding down the SPLIT button and the TONE/REGISTRATION button, press the keyboard key of C that you want located at C4 (middle C) of the left keyboard" and you should see a screen with an L (for Left) and a number (indicating the amount of your octave shift), as shown in the screenshot from the manual below. Although the English is poor, I think I know what it wants... but any time I try, it behaves the same as if I were only holding down the Split button (and not also the TONE/REGISTRATION button)... that is, whatever C key I hit (with those two buttons depressed) simply changes the split point to that key, rather than doing an octave shift. Has anyone gotten this to work? Any clue as to what I might be doing wrong? (It may be moot, because if this isn't saved as part of a Registration, it would be a useless function for me anyway, but I can't even get it to work so I can try it.)