"[C]overed employees accrue one hour of paid leave for every 40 hours worked, for up to a total of 40 hours earned in any designated 12-month period. Employers may also satisfy the paid time off requirement by granting, or 'frontloading,' all 40 hours of paid leave at the beginning of the designated benefit year. Employees must be permitted to carry over up to 40 hours of unused paid leave to the next benefit year, except where an employer frontloads the full 40 hours."