I'm new to Jira Administration and scripting so I'm not sure if this is even possible.
I have two Select List (single choice) fields, one with values 1...10, another with values 1...5. What I'm trying to do is copy the 1...10 field over to the 1...5 but divide by to, thus converting 8-10 to a value of 5, 6-7 to a value of 4, etc.
We have the ScriptRunner plugin which has the built-in "Copy custom field values" script, however that looks to be a 1 to 1 conversion for custom fields so I don't think it will apply any math to the conversion.