I thought I had come to the point in my life where everything made sense......that is until I got looking at RPO codes.

I've figured most of them out but I'm down to two that have got me stumped.

R7K
R9Z

I've figured out that R7K is "Control - Sales Item No. 36" and R9Z is "Control - Sales Item No. 100" but that means nothing to me.
So I'm wondering if anyone could tell me what these actually mean or perhaps how/where I could find out for myself.

Thanks.