I found these few RPOs below, some of which match yours, some don't. As was previously mentioned, GM tends to use "M" RPOs to designate the transmission, and from what I've seen, the "R" codes tend to correlate to dealer ordering options, which don't really impact hardware on the car.
R6K - PREMIUM PAINT
R6P - PREMIUM PAINT
R9F - PROCESSING CODE
R9L - SPRING WHOLESALE FLOORPLAN PLUS
R9N - HEATED LEATHER APPOINTED FRONT BUCKET SEATS
R9U - GM ACCESS - AUTOBOOK IDENTIFIER
R9X - XM TRACKING CODE