OK So what is an acceptable number; <5, 0, 1
?
It depends. I watch the percentage more than the actual number, since that's basically your lost profit. So for example, if overclocking by 5% hashrate leads to a 1% increase in HW and not a huge increase in power consumption, I watch the machine for stability to be safe but am fine with that, since the increase in efficiency outweighs the error loss.