How to adjust the reading in VOLT unit (Reading should be .05)

If you have pressed both buttons while reading displayed which means it will change the unit of measurement.
You can change it back to the correct measurement.
 
Kindly turn on the unit, blow into the unit.
Then when reading shows up while still displayed, please press both buttons together at the same time for a couple of times.
Then the display will toggle with different readings.
 
You can choose the one which reads %