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

I was offered 10 weeks of severance after 10 years as a janitorial supervisor, and I have a few days to sign. I have been trying to stay organised about it. 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 2 months ago, and it got easier once I kept a simple log of every call and form.