How to offset calculated sensor?

[mironoff2007]

Hello.
I have flvss sensor. After some time I got a problem with it. First and second cells voltage are wrong. First cell voltage = real_Cell_1_voltage - 0.3V , second cell voltage = real_Cell_2_voltage + 0.3V. Average between them is correct.

For Example :
Lipo in storage, all cells are 3.85v
Cell 1 = 3.55
Cell 2 = 4.15
Cell 3 = 3.85
Cell 4 = 3.85
Cell 5 = 3.85
Cell 6 = 3.85

Sensor screen has same values. I tried to offset cells values but I can't find the way how to do it.
I can add Custom sensor by ID and offset it, but each cells are obtained by calculation from "Cels" sensor with ID 300 inst 2. Calculated sensors has no functions to offset. I can add value, but I can't create sensor with consant mock value to add it to calculated sensor to offset it