The trainer instructions are assuming that you won't use rate switches (either because many basic radios don't have them, or because it's too much trouble for a beginner). I'd just set the low rate to the same as the high rate for now, and concentrate on flying. That way you can't get in trouble by accidentally hitting a switch on your TX. Later on when you are flying hotter planes (or doing silly things with the trainer), you can look in to using rate switches.