Hello!
I have a Victor 79A+ multimeter-calibrator, but I don't know if it will help you, the devices are different.
To enter the calibration mode, you need to press the REL and RIGHT buttons on the switched-off device and turn the switch to the parameter where you need to calibrate. Range selection - RANGE, scale start/end - REL, data saving - Hz. Each calibrated range is saved separately.
Voltmeter calibration example:
Range 0...5 volts.
Close the inputs - 0 volts.
Press - REL / go to the beginning-end of the scale /
Apply 5 volts to the input.
Press - Hz / save calibration /
Press - RANGE / select the next range /
и.т.д
Play around with the keys, your device may have other entry points into calibration. But be careful, mine has a three-key combination to reset the entire calibration, I got caught.
Удачи!