You can find the Link 2000 manual by using the link provided here:
Electrical Systems 101
You should also read the "Gotcha Algorithm" topic to avoid having the Link 2000 declare your bank prematurely full:
Link-series Charging Algorithms -- The "Gotcha" Factor!
IIRC, there is no voltage "calibration" on the Link 2000 (we have one on our boat).
It reads the voltages from the wiring
to the banks. IIRC it's from the wires with the fuses
to each of the two banks, not through the shunt.
What makes you think your voltages are wrong? Just guessing, but I'd bet you're reading the voltage at the banks with a DVM and comparing it to the Link 2000 voltage readings. In many cases, DVMs can be off the 0.15 you note on one of your banks, but 0.85 is MAJOR and the difference between a full and empty bank. Have you checked your wiring
I have not ever had this issue with our Link 2000.