You almost got it right. Here is the numbering system as I understand it:

The first knife made of any pattern is now stamped "Prototype". Let's say a 3.5" pattern is upsized to a 4" pattern, even that first 4" version would be stamped "Prototype".

Subsequent knives of a pattern would be stamped starting with "0" and then "1 thru 9" for following knives of the same handle material. Knives aren't numbered past "9".

Does that help? If I'm wrong, Tony might step in here and set us straight.