Ortur Y axis rotary roller setup

Hi All, I have the Ortur Y axis RR machine and somewhat confused about the setup in Lightburn.
Having enabled the RR, I can input all the dimensions apart from 1, can someone please explain how to obtain the missing one.

Example: Roller Diameter = 20mm
Object Diameter = 76mm
Circumference = 238.761mm (automatically inserted having set object diameter)
mm per rotation =???
Given the above information, what would the mm per rotation be and how is it calculated.

Thanks to anyone in advance,
John Wheeler.

Have you found your solution? Just got my Y axis rotary set up tonight. I’m needing some help setting up. What Laser are you using? I have a Ortur laser master 2. Not many people posting about the combo these 2 units. Any help or advice. Thanks

Take a look: Setting up Ortur YRR Rotary Device in Lightburn - YouTube
or here: Ortur YRR Rotary Roller Set Up | John’s Tech Blog

Have you gotten the info you need? I have same problem