Good question!
I do think that if the purpose of the police checks was to establish whether or not SB was in the habit of setting her clock 10 minutes fast (as opposed to establishing the fact that she had actually done so) then it doesn't matter that the clocks had been changed twice in the interim period. In fact it strengthens their case in that she had set it fast a further two times, just as she said she was in the habit of doing. But then she would, wouldn't she.
So what have we got, re timings if calls? Jeremy, EPHQ, Julie, SB, and Stanly. I would be HIGHLY surprised if Jeremy got the timing accurate. Having been in a similar situation, I know I didn't. The same could be said for Julie & co, woken from drug hazed sleep. Which leaves us with EP suggesting/encouraging/tweaking/coercing. Is it any wonder that we cannot agree on timings?