Ok, charge your battery up to full charge. Go to the bottom right of the screen and click Parameter Settings. Then click cell characteristics. Then scroll down to SOC Set. Enter 100% and click set and it will ask your for a password which is 1, 2,3,4,5,6. You have then correctly set the SOC to 100% and as the battery depletes then the SOC should be accurate.
I did say that the SOC should be accurate but in actual fact it isn’t really. Once the battery has settled from charging or discharging then you will get a more accurate reading. Don’t be too worried about SOC as your BMS will handle everything.
An example of this is yesterday I was testing my air con in my caravan and run the battery down to 89% within a short time with no load it had risen to 91%. I then connected some portable solar panels and took it up to 100% but at the end the SOC was reading 13.8v @ 100%. Within a short time SOC had dropped to 13.6v and still showed 100%. Just too a quick check in replying to you and SOC is now showing 13.3v @ 100%.
So charge your batteries up to full, let them settle for a while, then set the SOC.