Maybe the dial marks the distance from the edge of a sheet of paper that "Account Payee" is printed?
And the odd numbers refer to differing formats of pre-printed cheques?
Do you remember having to write "Account Payee" or "A/c Payee" between the cross lines on a cheque? It meant that the cheque had to be paid into a bank account, and couldn't be cashed.
It's similar concept to those hole punches that you can vary according to sheet size? A4, A5, Legal, Letter, etc.