The adjustment is literally a hair width adjustment at a time...LITERALLY. Turn the thumb screw a hair and wait a minute to see if the frequency of the tank matches the setting and creates a wave. If not, turn it another hair and wait a minute...etc.
The worst thing with the Tunze setup is it does not have a digital control with numbers from 1-999 for example. The stupid little thumb screw adjustment can easily be bumped then it's a lot of hunting again for the right "dial-in". At least with digital you could write down your setting, say, 734, and just reset it again.