That being said, you should be sure that you are being treated fairly and equitably. You should expect to receive similar severance to any other employee of your status that has been separated in the past. You will likely be asked to sign a general release in return for severance - make sure you have an attorney review the release. Finally, I assume from your handle that you may be over 40 - if so, you are a member of at least one protected class. If you feel you are not being treated fairly, you may have some legal recourse.
Note: I am an HR Exec and would be happy to talk to you live if you'd like more advice. E-mail linked above. Good luck.
My previous employer had an ongoing RIF event over the past 6 years. Severance was only changed during the new benefits roll-out, and everyone who was actually laid off, not fired, received it, as long as they signed paperwork that prevented them from suing the company.
Part of the severance time was a mandatory multi-week waiting period that was required by law when laying off a high number of employees. We typically rec'd 2 weeks per year, with 60 days of that spent in-company doing nothing but looking for internal/external work.
part of an RIF and the "severance" you are requesting is severance pay. If that is the case, I would submit a request to HR with a cc to the top Operations person at your site. No need, at this point, to involve an attorney. That may come later.
If the manual says that severance pay may be granted that means it has been granted in the past.
I come out of manufacturing (also in Illinois)and standards for severance are different for every industry. That said, you are a professional and 2 weeks per year of service is not unreasonable.