There are ten Master Levels. There are two tracks each player can choose from. There are eight tracks altogether (obviously, there is some overlap between the classes). So, there are a total of 80 Master Abilities, but you'll only be able to have ten of them yourself. (All 10 will be different and not the "bigger version of last level's" you were worried about.) You'll choose your track when you finish the first Master Level Trial, and subsequent abilities on the track will be awarded automatically.