Employees shall accrue (8) hours per month of service.  Employees shall receive additional leave by reason of tenure based on the following schedule of continuous City service and in proportion to the usual number of hours worked per year in their respective schedules:  beginning with the eleventh year (ten years completed service) through completion of fifteen years employees whose work schedule normally result in working approximately 2080 hours per year (40 hours per week) will receive an additional 24 hours annually, for a total of 120 hours, and employees with over fifteen years of completed service receive an additional 40 hours annually for a total of 136 hours.