I'm afraid I can't see how OzBob's explanation has anything to do with the item.
A compass repeater or a pelorus (totally different instruments) both need to cover the whole 360 degrees and would be graduated in degrees all the way around, they'd be useless with less accurate reading possible.
Quite how those helmsman's orders and procedures link to the item is beyond me, I can see no correlation at all and least of all how applying 20 or 30 degrees of rudder relates to graduations on a compass repeater.
Any more ideas?