@lewiss - there could be two zones on that terminal as there are no spare terminals. If you haven’t moved all the wires from the Hunter Pro to the Rachio then I’d take out the pink wire and run that zone to see if anything waters. Then repeat with the black wire out.
If the Hunter Pro has already be de-installed, then I’d connect the black wire to an unused Rachio zone and run that zone to see if anything waters.
I agree with @DLane, I’m guessing 2 of your zones are doubled up. I assume that you have a 16 zone Rachio, so you could separate them into their own zones, just run each one to figure out what it waters.