LX-Nav S80 settings

I just installed an LX-Nav S80 and remote stick controller, and while I am mostly impressed with the hardware, the operating manual is sorely lacking in many areas.

When trying to enter the value for ballast weight, you have a choice between overload, weight, lb/sqft and kg/m2. Absolutely no explanation is given in the manual about how to use these numbers. I can understand lb/sq ft and kg/m2, but this isn't how I normally load my glider. And I have no idea what "overload" might refer to.

I just want to set my empty glider weight and pilot weight with chute in the appropriate fields and then enter the weight of the ballast I intend to carry.

Do I enter the gross glider weight or the ballast weight added?

Any help would be appreciated. As I get more involved with the mysteries of the S80 and its woefully inadequate operating manual, I will undoubtedly have more questions.