I've been reading the manual all day and i cannot make heads or tells of this. In Chapter 0 page 18 it states Determine the Failure Rate: Random failures require that the user select a

It means: over infinite time, you should expect to get - on average - 1 failure every 10 hours.Internally, I expect they use a pseudo-random number generator to determine if a failure occurs. I don't know how often they take a sample, but lets say they sample every second.Which means 10 * 60 * 60 = 36000 samples in 10 hours.Hence, the chance of a failure happening in any given sample is simply 1/36000 or 0.0028 %If you set the option to 3 failures every 10 hours, the chance increases to 3/36000 or 0.0083%Hope that make some sense to you. :)- Bill