How is CG coming up with J13 in this particular case, can you please explain in some detail to understand how the various hierarchical systems make a decision among the 290+ legal moves in this position?
detailed explanations of how CG chose J13 are provided in my paperhttps://papers.ssrn.com/sol3/papers.cfm
and my videohttps://www.youtube.com/watch?v=Nns7004 ... a3Hl1X_v-S
your question seems to contain an implicit assumption, namely that CG decides between all the legal moves. It doesn't work that way (neither do any other bots, including Alphago).
CG looks at what it thinks is the big picture, computing clusters, groups, territory and influence, from which it figures out what it thinks is happening, and then decides what strategy to adopt. this becomes its goal, which its planning methods try to achieve, in so doing creating a tree of subgoals and so on down to the level of moves. for each of the move candidates it comes up with, it looks to see what it thinks the opp would play in reply and whether it thinks that would refute any of its goals. and then it looks to see whether it thinks it can refute that refutation by its next move and so on.
Note particularly that CG found a justification for J13, namely that it thought white would reply at L12 and then black could play the key killing move of L10 on its next turn. i had simulated CG by hand, and didn't go into other variations CG might have considered (there wouldn't be many).
how deep and how wide CG's highly selective search continues depends on how much time it has to make a move (i haven't described algorithms for that; my intuition is that it may be necessary to include Monte-Carlo search as well, since one cannot expect to be able to confidently predict an opponent's moves).
in general, CG is a software (design) embodiment of a decision-making methodology called "satisficing" that one of my heroes, Nobel laureate Herbert Simon, described. Whether or not you are interested in AI or economics or cognitive or behavioural psychology, i strongly recommend googling Simon as his theories are jolly useful and practical insights into how people go about making decisions, whether or not they are aware of what they're doing - and even if they think they're doing something different, like optimisation!
in 1975 i think it was, i had the great pleasure of chatting with Simon about my own work; he used to spend most of his time telecommuting to Carnegie-Mellon University from home but came in to meet me in his office. i thought telecommuting was a terrific idea and there and then it became my life's ambition to find a job i could telecommute to whilst living in a place of my own choosing (like Raivavae, because from the nautical chart it looked to have a perfect cyclone shelter at just the right latitude for getting the best food crop growing climate on Earth).
I never did find such a job, but i did visit Raivavae, although once there, i was persuaded by a Polynesian lady to stay on her island - Tupuai - a perfect example of satisficing in real life