Is it possible? Reading RMS value at 0.02% of range? When manufacturer states in manual accuracy from 5% to 10% of range is 0.3%+100 counts?
Yes.
Those numbers aren't "garanteed
inaccuracy", they're the outer limits of the bell curve on the production line.
Those bell curves also allow for extremes of temperature, and temperature makes a
big difference to handheld meters with this many digits. If you're measuring at the same temperature as the factory's calibration room then you'll get much better accuracy than if you're measuring at freezing (or hot) temperatures, which is where those outer limits of accuracy will come into play.
Bottom line: In practice, and at ordinary temperatures, these Brymens will do
much better than those specs
. I've compared mine to a fancy 6.5 digit bench multimeter and it matched it perfectly.
What for are manuals then?
To know when there's something seriously wrong with the meter.
(and when the manufacturer will accept a return under warranty).