I would like to interpret my ammeter. I don't understand what the point with the numbers 2,20,200 means and what is the exact current I am measuring. Thanks
You've carefully trimmed the photos so we can't see where your probes are connected.
When using the 2m, 20m, and 200m ranges (switch positions) the red meter lead should be in the "Volts/Ohms/mA" socket, and the black lead in the "Com" socket. For the 20A range, the red lead should be in the "20A" socket.
I suspect you are using the "20A" socket for all readings. If so, the readings on the mA ranges will be meaningless.
If so, the correct current is read with the range switch in the "20 A" position, and the current is 0.05 Amp, or 50 mA.
That is the display you would get with a constant voltage applied to the meter (probably 0.5mV).
The input current would vary with the range setting.
You may be getting some kind of false reading due to EMI since the current drawn from the power supply is switched at relatively high frequency to feed the stepper motor.
I have a feeling that meter is only accurate to three digits, the forth being the 5 which is probably either 0 or 5. It may have only 8 bit sampling resolution, or effectively 9, which would pretty much put you in that ballpark.
When you up the scale the rounding error then moves up from the mA range up to the tenths of an amp at the 200A scale.
As such, the least significant bit is pretty much useless on it's own. It shows you the least significant bit is indicating that digit is more than zero and possibly as much as half that digit point.
This is really only a guess though, but it sort of fits the symptoms. It would be interesting if you can force it to show other than a 5 in the last digit.