I'm not sure I entirely understand your question, but it works something like this.
The school completes comes up with a budget that includes tuition, books, and living expenses. The FAFSA determines your EFC for the year. Your school then takes the budget and subtracts your calculated EFC to determine your need. They then use that 'need' to determine your mix of institution grants/loans and Stafford subsidized/unsubsidized. There is nothing set in stone as to the amount they can offer (although they can't add more Stafford loans then would be allowed by their calculated budget).
Having had a full time job (and perhaps some savings) your EFC will likely be high and so your 'need' will be lower than others in you class. However the financial aid office can alter things a bit. For my first year of medical school (prior to which I was in a high-paying job), my EFC was higher than the entire school budget and yet they still offered me some Stafford loans although it was lower than the maximum of $38,500 and there were no subsidized loans offered. For my second year of medical school I had put most of my savings into buying a house, had little income and therefore had a low EFC and qualified for the full subsidized loans ($8,500) some more unsubsidized and even some institutional grants.