Don't know how much this has to do with it, but computers think/speak in binary - 1's and 0's. You can count from 0 to 63 using 6 bits, that is 000000 thru 111111. To get 64, you need a seventh bit (1000000). Often times when computers do goofy things related to math, it happens on the factors of 2 (1, 2, 4, 8, 16, 32, 64...). If the computer - due to a programming error - is only reading the first 6 bits of the mileage data, it would go 0 - 63 then recycle. It could be some other combination as I'm not sure how they'd handle the decimal.

*** Retired after 65,000 outstanding miles ***