> the digits for 3 have either three horizonal strokes ౾ or three vertical strokes ౻, and the others similarly. I have an idea that the alternating vertical-hor

> the digits for 3 have either three horizonal strokes ౾ or three vertical strokes ౻, and the others similarly. I have an idea that the alternating vertical-horizontal system might have served as an error-detection mechanism The Chinese Suzhou numerals use alternating 〡〢〣 and 一二三 but for a different reason: "21" is written as "〢一" instead of "〢〡" which can be confused with "3" (〣) from https://en.wikipedia.org/wiki/Suzhou_numerals https://en.wikipedia.org/wiki/Suzhou_numerals