Should I negotiate my severance? - any advice?

The company sent a severance agreement with a release of claims, and I am unsure what to do. I have read a lot of threads here and could not find my exact situation. There is a non-disparagement clause. 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.