BQ27426: bq27426 FC bit issue

Hi, 

Currently i'm learning BQ27426, in the datasheet, it says:

I can't understand the logic behind this. FC Set % default value is -1, so when SOC reach -1, FC bit is set. How does this happen?

In my opinion, FC set % should be like 99.9%, and if SOC reach 99.9%, FC bit is set, and that means the battery is fully charged. Could you tell me where i'm wrong? 

Thanks.

Best regards

Mason