[Airstreamer]

I set mine at 100 as well. I didn't want to drain a new lithium battery pack.

 

[Airstreamer]

The OP wrote that it says to discharge battery to zero and set the monitor then to zero.
Makes sense. It would then measure the amps going in to get a reading of capacity.
If you charged the battery to 100 and set it to 100 and entered in the total amps per the literature you may never have an accurate reading.

I'm not 100% sure, but even if you are off initially the whole thing should calibrate the first time you are sitting at 100% and still charging.