I don't think there is a document of the codes, but check out this old post that lists out the feature rights codes. Is that what you are looking for? 

Thanks! That really helps. Now, is there a document or guide where we can find what those numbers mean? How can we convert them to a list (like the one displayed with Decode Flags)? We need to generate a report from Audit trail and export it to .csv, but we need the descriptions and not codes.

Any suggestion is appreciated.