A tiny level raise on the line in bus during playback

I have asked Presonus about this, but they could not help me, so maybe someone in here knows something. when turning up volume knob for my headphones on my audio interface, I see a tiny level raise on the line in bus in cubase during playback. Nothing else is connected but my headphones. I tried recording to test if the tiny signal is being recorded, but the signal is too low to be registered, or maybe the signal is a graphic bug or something. The secondary mixer for the Presonus Studio 192 interface outside Cubase, it does not show anything on the line in bus. So I do not think, that it has any influence on recordings, but why and what? Does anyone have any idea? A bug?


What is connect to this Input bus?

You can record the signal, and maximise it later, to know, what happens there.

Nothing is connected to any input bus.

Did you try to record it, and maximize, to hear and see what’s going on?