Line Manager and HR getting different values for years of service formula

Summary:

I am working on a report that lists employees that have upcoming birthdays and upcoming anniversaries in the next month. If they have a birthday, that birthday is listed. If they have an upcoming anniversary, that anniversary is listed as well. If they have an upcoming anniversary the report also has an additional column that shows how many years of service they are celebrating. I pulled the report for myself and also sent it to a Line Manager as an agent to ensure that the data is being reported out accurately. Everything was correct except for the years of service