It appeared to me that once you work out the measurements, and go to your dividing head reference manual, you set up the adjustable “reference counter”.
It’s just a matter of being very consistent and accurate as you rotate your gear around - which is the problem the dividing head is intended to solve!
On our first pass, we cut very light “indexing marks”, and ensured they were in alignment when we got back all the away around. Once we proved this, and that we had the correct number of gear teeth (very important!), we were confident in the setup - and cut the teeth for real!
Afterwards, we flame hardened the gear, to give it better wear resistance.
It was a fun project!