Severance offer, what should I ask for? - 12 months and counting

I was offered 11 weeks of severance after 11 years as a pharmacy technician, and I have a few days to sign. I have read a lot of threads here and could not find my exact situation. I do not want to leave money on the table.

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.