Severance offer, what should I ask for? - 24 weeks in

I was offered 3 weeks of severance after 3 years as a quality inspector, and I have a few days to sign. This is my first time dealing with any of this. I do not want to leave money on the table. Did anyone negotiate and succeed?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.