4 dB Signals above the Rec Gain?

What do these 4 dB signals ( 0dB, -3dB, -6dB, -20dB) located above the Rec Gain Knob?

Should they be light up yellow, when i play with my MPC Pads?

When should be the dB`s displayed?

I give you a hint: it's located over the mic / phono in switch and the record gain

It therefore has nothing to do with the Sound Volume in the Program Mixer....! Thanks Acura.