Often, the totals would differ, strangely, by a number divisible by 9.

For example, our total might be $ 56,023.00 and theirs $ 56,068.00,

with a resulting difference of $ 45.00.

This is caused by a simple "twister", for example when a typist entered

$ 27 instead of $ 72

$ 38 instead of $ 83

$ 49 instead of $ 94

$ 50 instead of $ 05 . . .

I also noted that these plurals of 9 can quickly been computed

by taking the difference between the two digits and multiplying that by 9.

For example, the number 38 will be associated with a twister of (8 - 3)* 9=45

Check out: 38 and 83 differ by 45.

After a while, it becomes fairly easy to spot the error -

that is, as long as there's only a single error.