Toggle Count-in    ⇧K

Turn ‘Count-in’ on and off.

Use the metronome in Logic Pro — Apple Support

Click the Count-in button in the control bar to have the metronome play a predefined count-in before recording starts.

“K” is for Klopfgeist | Logic Pro

Klopfgeist is the software instrument that powers Logic’s Metronome function. For many of us, there’s not much more to think about with the Klopfgeist other than enabling the Metronome and hitting “record.” But there’s plenty to dig into with our trusty and unwavering click. Whether it be for utility or creativity.

The best translation of Klopfgeist I have seen is “rapping spirit”.