I have the digital controller so I'm not familiar with what you have. It looks like that controller has a 4 degree differential which you cannot change, so a setting of 34 should mean that the freezer will kick on at 34 and cool to 30. How quickly the air goes back to 34 is based on your freezer and the outside temp, etc. It sounds like the temperature dial on those things can be a bit suspect based on some reviews, so the controller set to 34 may actually be 38, but it also sounds like the error should be consistent. Remember than the temperature of your beer doesn't swing as largely as your air temp.