At its most basic, meaning just is the set of concepts and behaviors that allow correct manipulation as judged by some standard. So in this case the rules of the game have meaning within the context of a game of Go as they allow for correct manipulation of the game state. That what constitutes valid board states was derived from conscious entities isn't relevant here. The rules of Go have meaning (allow for proper manipulation) within the context of the system of valid board states and transitions between them.
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