How much level do you recommend reaching on the level meters?

We recommend you don't exceed 12 dB (red) on the channel level indicator and [6.0 dB] (with red frame) on the peak level on the screen.

As for the peak level on the screen, the [CLIP] indicator will quickly blink to indicate internal digital clipping.

For details, see the [Channel section/master section] in the [Audio output] section of the Instruction Manual.

You can read the Instruction Manual [here].