Reply #4: This is the key

[Boredtodeath]

from his original article:

In many computer programming languages, integers are by default signed... positive or negative. This is the case in the C language, which was most likely used for the voting machine. If the programmer is unskilled enough to write a hackable machine, then it is also quite likely they used the default for the integers rather than realising that votes would never be negative, and explicitly using unsigned integers. (Actually... totally regardless of whether the programmer used signed ints or unsigned ints, the actual mistake the programmer probably made was not using %u, and using %i or the very commonly used %d in their sprintf statements instead... which would have caused +4 billion to be logged as -25 million.)

Combine that with the KNOWN information that %d (or signed integers) are required in the systems because of MANUAL ENTRY, and it's a done deal. Using Manual Entry, negative numbers are REQUIRED:

http://www.countthevote.org/manual_entry/manual_entry.htm