I have read that before but my hash rate is being reflected in the pool. The average over an hour usually runs about  350 ghps. I agree that the average from to pool is the only thing that really counts but if you can make accurate predictions repeatedly from that squiggly line then it is good data. If i was averaging 395 ghps i would no be worried about it but my average payout is dropping constantly, but slowly. When i first got the machine it was running at an average of 410 ghps not counting the crashes when i was not home to fix it.