So.... In a lot of these cases the system wrongly reported money missing at these lower levels. It seems these numbers should have rolled up into sums at a higher level that also showed losses and they prosecuted people. But the money was never actually missing so where did it go? Hmmm?
If a Post Office had £20,000 in takings on a day, but the buggy system reported takings of £30,000, then that's £10,000 of money reported missing, which the postmasters were prosecuted for stealing.
But that £10,000 didn't "go" anywhere. It never existed.