This section applies only in St. Mary’s County. The Sheriff of St. Mary’s County shall receive an annual salary of: $100,000 for calendar year 2015; $102,000 for calendar year 2016; $104,040 for calendar year 2017; and Beginning in calendar year 2018, equal to the salary of a Department of State Police lieutenant colonel (step 12). The Sheriff shall devote full time to the duties of office.