The support page provided by the Replay Music developers contains user guides and tutorials on how to work with the application. You can start with that in order to learn how the tagging work for the music you have or recorded.
Support page: http://applian.com/replay-music/support/
I couldn't find anything related to REL 7 term that you mentioned in your question. Also, based on my experience with music tagging, not always works perfectly because I've encountered situations when an original track wasn't recognized properly by the audio tagger app.