Severance offer, what should I ask for? after 5 years as a janitorial supervisor

The company sent a severance agreement with a release of claims, and I am unsure what to do. 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 14 months ago, and it got easier once I kept a simple log of every call and form.