The manual just says this: "The Time Signature can be set on a preset-by-preset basis, or changed on the fly using MIDI commands. For quantization to the beat rather than to the measure, set the measure to a single note (eg. 1/2, 1/4, 1/8, 1/16)." and in a reply from customer support they said: "You will need to reference your master device to send time signature changes. Many devices are different but the Looper can accept these time signature changes if the time signature change is sent correctly. "
I have looked up MIDI Time Signature and it is freaking mind bending, but I think I understand. One source threw me off, but this one explained that the 5th number set (cc) needs to be converted to hexadecimal. Going to try this and see if I can get it to work
FF 58 04 nn dd cc bb Time Signature
The time signature is expressed as four numbers. nn and dd represent the numerator and denominator of the time signature as it would be notated. The denominator is a negative power of two: 2 represents a quarter-note, 3 represents an eighth-note, etc. The cc parameter expresses the number of MIDI clocks in a metronome click. The bb parameter expresses the number of notated 32nd-notes in a MIDI quarter-note (24 MIDI clocks). This was added because there are already multiple programs which allow a user to specify that what MIDI thinks of as a quarter-note (24 clocks) is to be notated as, or related to in terms of, something else.
Therefore, the complete event for 6/8 time, where the metronome clicks every three eighth-notes, but there are 24 clocks per quarter-note, 72 to the bar, would be (in hex):
FF 58 04 06 03 24 08
That is, 6/8 time (8 is 2 to the 3rd power, so this is 06 03), 36 MIDI clocks per dotted-quarter (24 hex!), and eight notated 32nd-notes per quarter-note.