California excludes total unemployment. 

But CA starts with the Federal AGI which already has up to 10,200 already excluded from it, so it needs to be added back or youd be deducting the excludable federal portion twice.

If you've answered this question once, you must have answered it -- well, at least twice, but maybe closer to a dozen times.  And every time I read your answer, I want to ask "but where does it get subtracted out again?"  Because someone who has to ask, may not be able to find the right form and line number.  

"treated as a positive number if the amount is negative. What does it mean?"

It means the field is already dealing with Subtractions or reductions, so don't also make a negative entry.