The "Learn" function has nothing to do with the tuning. It refers to the digital rolling code that is used to keep the receiver and the transmitter in sync. These rolling codes are used instead of a fixed code so that an attacker cannot simply record the signal off the air from your transmitter and then replay it later to make your door open. The code needs to change every time. The Learn function just tells the receiver to listen to the next thing it hears off the air and accept it as the correct rolling code, and then continue in the sequence of codes from there on.
-Robert Scott Ypsilanti, Michigan