Are you using the metronome? If you are in the metronome page you can use the green knob to change to a “Beat Match” mode that lets your tape track roll in sync with the metronome.
Usually what I’ll do is have the tempo set in beat match mode and now the white markers in your tape mode represent a bar line. You can use “SHIFT + >” to make your playhead snap to a bar.
Set your in point using the “1” key marked “IN” and your out point using the “2” key marked “OUT”. You now have a perfectly looping section of tape that is matched to the tempo of your metronome.