Due to the design of some multimeters, a reference value is needed when measuring large resistance (200M). When the test leads are shorted, a resistance value (such as 1M for a 1999-count multimeter or 10M for a 19999-count multimeter) may be displayed. This value should be subtracted from the measured value to obtain the accurate resistance.
Why the reading can not be reset for 200M resistance measurement when the test leads are shorted?