The question is: at what level the decision about look at the clock arise and/or makes the specific hour "visible" to the observer. What is the real level of awareness which is the source of decision about checking the time on the clock and with what is correlated?
Generally, I understand your way of thinking, and it is sensible, however only when you settled certain assumptions first. You made the assumptions that we have to do with a real existence pattern (when at the moment we do not be sure about that), an urge (when we do not really know whether Gruchaa feels something like this), also the way of re-phrasing - we do not really know what kind of thinking about the new task Gruchaa would have. If he would start thinking about that in the way you describe it and as you questioning it, entirely understandable, we come back to the beginning of the considerations, where lies the cause of the phenomenon and whether we factually have to deal with some phenomenon.
The first thing we can do as the first step would be to get objective observations. In this case, Gruchaa should be observed by outer observers in his natural state, without any commands for him, the best if he would be unconscious about that somebody was watching him. So we back to the initial "80%". Such observations would have the aim to check how many observations he does and what is the time on the clock he looks at in these moments. And then data should be analyzed in the context of different correlations occurring.
Of course, nobody would do anything like this. This is just a thought experiment we go through this discussion colliding our ideas. In fact, for practical reasons, the best for Gruchaa would be to do not care about such check-time coincidences, do not put energy into it, by stop thinking about it and stop being intrigued by such coincidences.