Voltage calibration: "voltage divider" v. BATT_VOLT_MULT

Trying to get consistency between MP and voltage provided by FLVSS module (ctot). I have a Mauch PM.

I do not understand the relationship between the parameter BATT_VOLT_MULT and the MP “voltage divider”. Does changing one affect the other?
EDIT: They are the same thing but with different names! I changed them both in MP and the change was reflected in the other.

Calibrating the voltage is typically done with no load. Should the voltage readings from MP and FLVSS match each other under load e.g. when pulling approx. 15 amps when hovering?