I seem to remember once being told that gross is what you expect to see from an average aircraft of your type, on an average day, with reactions from an average pilot.
Net is those conditions factored down to a probability of one in ten to the sixth - which won't happen so often - but which will cover (except for the ones which end in accident) the worst case.
I'm prepared to be corrected on points of detail - but, basically, net is a statistical extrapolation of gross - and I'm sure that one in ten to the sixth comes into it somewhere.