How do you decide the amount of ssi I'm entidled to receive... I get 323 ssa 157 ssi have no savings

We don't decide it, the Social Security administration does. If you need to understand how its calculated, Check the SSA web site or your local office.

As Scott said... a major factor is your earning history, and most the last several years before you qualified. The less you made the less you are entitled to receive. The fact you have no savings has nothing to do with it.

The second amount is determined by the state you reside in.
The first amount is determined by your work history. If you were married for 10 years or more, you can get some of your spouse's SS.
Yours is extremely low, suggesting that you didn't work much at all?
480 total means you qualify for every benefit there is, from housing and Medicaid (to cover what Medicare doesn't) to food stamps. The income of anyone you live with is counted as income for you on any of the state (welfare) benefits - basically anything except SS and Medicare.
I hope you are talking to a worker at your state offices about all this.