UR44, Line-in turned down, yet there's a signal?

Hi,

I am afraid I am a bit confused with the UR44 and its DSPmix software.

I don’t need any kind of direct monitoring at the moment. DSPmix ist set up with all channels muted (M) and only DAW open (S), see attached IMG. The external instrument is connected to Line-In-1. Yet even with its levels knob completely turned down I am receiving the external synths signal at about -30db in the DAW channel? Shouldn’t it be completely muted until the level knob is turned up?

Any idea/help appreciated.

Thx.

Bump. Anyone?