Severance offer, what should I ask for? - 2 months and counting

I was offered 17 weeks of severance after 17 years as a retail manager, and I have a few days to sign. It has been weighing on me all week. It includes health coverage for a couple of months.

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

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