If you use Tap Tempo, the slowest setting is Whole Note which while give you a bar in terms of time.
If you need slower rates, choose Whole note, check its value in Hz, set T_Rate on OFF and set Rate to the value you like in Hz.
Example:
at 120 bpm a Whole Note is 0.50Hz. If you want 4 bars > 0.50:4 = 0.125Hz.
There is no way at the moment you can have slower values than a Whole Note using TTempo.
Best
I
