The "accounting gimmick" that footnote 7 refers to is the use of the sign bit to add an extra instruction in a specific case, giving a total of 33 instructions.

The "accounting gimmick" that footnote 7 refers to is the use of the sign bit to add an extra instruction in a specific case, giving a total of 33 instructions. https://www.cambridgescholars.com/resources/pdfs/978-1-5275-0650-3-sample.pdf https://www.cambridgescholars.com/resources/pdfs/978-1-5275-..., table 1-2 explains it.