Each shaft section (left and right) contains multiple load cells which are used to measure the force being applied to the paddle.
The output of a load cell when the shaft is experiencing no force is referred to as the Zero Offset. Each load cell has an associated zero offset.
There are four load cells on a kayak power meter and they have been designated A, B, C & D for reference.
The Zero Offset of a load cell can drift a small amount with a change in temperature. This is why manufacturers of power meters typically recommend performing a Zero Offset calibration on a semi-regular basis.
The Zero Offset of a load cell will be between -2047 and 2047. A typical Zero Offset will change no more than 2-5 units between calibrations. A difference of 10 or more is an indication that either a bending force is being applied to the shaft; that there is an issue with that particular channel or that you recently travel from an extremely hot or cold climate.