I see now in manual,it says:
"Check that the value of the SET-BATTERY parameter
corresponds to the nominal value of the battery.
Check that the value of the TESTER MENU / BATTERY
VOLTAGE parameter is the same as that measured with
the voltmeter. If it does not match, use the ADJUST
BATTERY function to correct the value."

And this has to be done with ETACC software tool and SST interface cable kit.

I'll check parameters next time when I visit the customer.

Tnx for directions,Nero