Ur-44 input gain on ipad/auria

I am using my ur-44 in cc-mode with auria app on ipad2. With 4 mics connected.
I found the sound picked up by the mics still output sounds even I turned the mic gain knobs all off on the UR-44.

I muted all mic channels on the dspmixfx app. On Auria,I enabled the “rec” button then I can monitor signal from mics. Sounds also can be muted on auria.

I expected it should be no signal input when I set the mic gain knob to 0 on Ur-44.

Do I get a defective UR-44? Hope someone can help…many thanks~

One more thing. There is no input signal when I turned gain knob to zero when using with my macbookpro.