Filing a Part Time Unemployment Claim with a 2-Day a Week Job

My question involves unemployment benefits for the state of: CA

I am familiar with filing with the State of CA as I had the misfortune of being laid off in 2010. However, that was with a full time employer, and now I am facing a part-time layoff, making far less per hour.

My SBP is $3,620, allowing me to collect approximately $556/mo. If this is combined with my standing 2-day a week job, I will take home appx. $1300/mo. which is the bare minimum I can live off with rent, bills, food and transit.

Do I have to claim preexisting part time employment? If so, how much will my claim drop if my preexisting income is almost the same as my claim?

I read this in the Guide To Benefits on the CA EDD page:
If your weekly earnings are $101 or more, the first 25 percent does
not count. The amount of earnings remaining is subtracted from your
weekly benefit amount and you are paid the difference, if any.

Does that mean if my weekly benefits are $139, and I earned $196 before taxes at my other part-time job, that I "don't count" $49, but $147 is subtracted from my $139? How can someone live on -$8/wk in benefits?

Your math is correct. Your UI check would be nonexistent.

It's worse in most other states. Once the PT job gross is greater than or equal to your weekly benefit amount, you get zero. At least in CA, you still get your $25 or 25% exclusion whichever is more.