Severance offer, what should I ask for? after 13 years as a data-entry clerk

My manager said the package is final, but the letter gives me time to review. It has been a long 6 weeks. It includes health coverage for a couple of months. Did anyone negotiate and succeed?

Thanks for writing this out. I went through something close to it 8 months ago, and it settled down once I kept a simple log of every call and form.