Volt meter from group buy

Hi! Those who have volt meter from @ajaynagra group buy, how do use it ? I mean it shows 0% all the time, when I press button on the back it shows volts. O.k volts are correct, but when I switch off battery, next time when I turn battery on it resets to % again. I need it to stay on volt reading all the time I don’t care about % reading.

On the back is button, but there is also another button( same but,there some parts missing) picture:

Maybe that other button is for programming? Because that first button is only change % to volts and turn off device.

You hold in the programming button when turning it on and it goes into a different mode. Then from there youll have to mess around with it as I havnt had the time to get it to onyl show volts.

I just tried to hold that button when turning on, it does nothing, everything is same as just turning on normally. Why there is that second button that have parts missing in that picture?

Theres a thread about.them. Search baiwei or similar.