WHAT DOES CCI 209 MAGNUM PRIMERS IN STOCK MEAN?

I obtained a simple optima, not an elite, about six-7yrs in the past. I attempted many different models of primers in it. I could about six rounds from your typical CCIs or Win magnums after which you can the primers would get packed in with carbon. They were being very difficult to extract! With most other makes 2-3 shots would have to have resour