Cell Balancing with LTC6812-1

Hi everyone,

I am trying to implement passive cell balancing with using external discharge circuit. As I read the datasheet of LTC6812-1 we need to configure DCC bit for the cell we want to discharge. 

I looked into the configuration register group A and B, and I noticed we have DCC0 to DCC15. However, we are monitoring only 15 cells with this LTC6812-1. why we have 16 DCC bits?

If I want to discharge cell1, should I set DCC0 or DCC1? 

I also have one more question. In my discharge circuit, I am using 20 ohm resistor in the discharge path. But the discharge current for me is too small. It is around 1mA. What can be the reason for it?

Thank you for your help in advance.