Severance offer, what should I ask for? - 5 months and counting

My manager said the package is final, but the letter gives me time to review. There are 6 people counting on me, so I am trying to be careful. I do not want to leave money on the table. Should I see a lawyer?

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.

Keep everything in writing and save the confirmation numbers. It saved me later.