DJM350 - settings?

Hello Pioneer,

When I turn on my djm 350 while holding these buttons: usb stop, search forward, search backwards

I get into some sort of menu where the top red master light is lit, and the bottom 2 green lights are lit (also from the master channel). Then I can 'adjust' the green lights by pressing search forward / search backwards. Now that I discovered this on accident, where is this for?

HeroS