(a) Operation is the same before, in the subordinate menu of calibration, use
[↑] or [↓] to select (4) AC H/V Cal. LCD display as following
(c) Press S1 [UP] or S2[DOWN] to adjust code, let the reading value match or
closer to the standard voltage as much as possiable
(d) Also you can press S4[AUTO] to automatica setup code
(e) After setup finished, press S5[DONE] to save
(f) If you want to abandon data, press S6[QUIT] to exit from this screen