And a booking class is not the same as a fare basis. All a booking class availability does is open up a suite of fares, via one or more fare basis, and this where the rules and change conditions all sit. If it is R0 it just shuts off the suite, and what is in that suite is in any case date / availability dependent. So the fact that your ticket is in R says almost nothing about what you can expect in this situation. RLW8E7S2 on the other hand is far more informative.