Q on the Digital LED Voltmeter PRT-14313

Hello all, my Q if anyone knows - there is a tiny smd potentiometer on the back, does this adjust the led brightness, or perhaps the voltage reading, or something else? - thx

It is used to calibrate your deviceā€¦use a multimeter and test a known voltage, then apply that to your screen and turn the screw (if needed) to make the reading match the previous measurement (known voltage)