Looks like the cell number to place the next symbol into. The one thing that I’m not sure about is if the position is 0 or 1 aligned (0-8 or 1-9)

assuming it’s zero aligned, here’s a worked example:
in state: ---------
if recommendation = 1 then
out state: -X-------

Edit: Running though several games using the assumption that the response is 0 aligned validated the assumption