Should I negotiate my severance? - what worked for you?

My manager said the package is final, but the letter gives me time to review. I do not usually post, so bear with me. I do not want to leave money on the table. What did you ask for?

Ask for the offer in writing and do not sign on the spot. A day or two to think is normal.

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