Hey Ron,
We performed a data regression to determine the formulas by evaluating quite a few data points. The constant values are conversion factors, essentially constants.
It roughly translates to the average number of Page Touches that an average message would generate in its lifetime including delivery, read, move, delete. Again this is a measured average and is not theoretical. The exponential factor (cache^-.65) corrects this and takes into account the fact that the cache allows pages to remain in memory and thus reduces IO as the cache gets bigger.
Hope this information helps,
Ross
Microsoft
