Its a magic of digits, you connect dmm to something and numbers changing, so you sitting relaxed .... drinking coffee (or stronger), watching numbers. Like some love a open flame, or petrol-head smells gasoline ..... radiohead likes numbers , it nothing special. Then woke up, switch to 3 digits and start to poking around; as 6 digits slow, making garbage, and tend you to zoom out.
One of my schematic was sensitive to moving finger around changing output to +0.6 mV DC. that not suppose to. it appears of self-oscillation, funny thing it kills when scope was connected, so high resistance DMM can reveal it. that the only case was, when 5.5 helps, and yes set in manual for 30V range you measure literally everything. but i hate not having null diff. in 3478a - that so useful sometimes.