Power draw / display of CT-3

mrspirytus

Hello,

I am running 100056 firmware download https://yk-lab.org:666/index.php/shizuku-firmware/
I noticed today something strange with my CT-3. I have been using it for monitoring and measuring current/power draw from various devices.
When just plug in USB-A cable to the female end and nothing else is connected to CT-3 ( The male USB-A is also not plugged into anything), I see TC-3 powering up. But what is strange is that current usage on-screen hovers around 0.030A / 0.158W. Since nothing is plugged in why is this not zero? I do have Fan attached to CT-3 with its more douth board. Is that was is causing the draw?
Right now I connected Raspberry Pi Zero and trying to see how much power it is using and since unconnected CT-3 shows such a draw, how can I calculate actual connected unit power? Subtract manually 0.030A / 0.158W from what is on display? Is there some hidden "zero" function?

Thank you