Sick Leave Conversion, Scheduling. Employees may convert three (3) days of sick leave (24 hours) for one bonus vacation day (8 hours), provided that only sick leave over 960 hours may be converted to bonus vacation days, that no more than five (5) days (40 hours) of bonus vacation may be obtained in any one calendar year, and that bonus vacation shall be scheduled the same as other vacation. Granting of bonus vacation shall be at the sole discretion of the Employer so as to maintain proper staffing. In no case may the sick leave balance after said conversion be less than nine hundred sixty (960) hours.