BTW this is why numbers in contracts are often written “1 (one)”: because in the age of pens it was easy to change “1” to “10” or “4” or “one” to “none”

Also why checks do this — checks are actually simply contracts, which were standardized in the US a bit in the 1920s (you’d get a check form, fill in your name and the bank name, then the amounts, etc; current check design With preprinted bank info dates back I believe to the late 1960s.