Service Months can be found when you click "View Leave Balances" from the dashboard. Service Months refer to your employment service credit (your current instance of employment at UC Berkeley). Your Service Months are used to determine your vacation accrual rate.
If you worked at a different UC location before UCPath was implemented, that service will not be reflected in UCPath (although all service at UC locations will count towards your retirement service credit - contact Retirement Administration Service Center (https://ucnet.universityofcalifornia.edu/contacts/rasc.html) at (800) 888-8267 for information on your retirement service credit).