Where to find what the numbers mean on FBA return packing slip??

I am still learning FBA. Can anyone explain to me like a 7 year old what the VRET ID and RA# mean on a packing slip of a returned product?? Also, what does the LPN mean? I received some of my brand new product back from FBA (that they requested). Its got a sticker that says LPN AC 90190 then 4 numbers in bold. The packing slip say the products are damaged. They are not. They are brand new and in the original packaging. How do I figure out what's going on?