An employee may accumulate unused annual leave and may carry over from 1 year to the next year up to 75 days or 600 hours of that unused annual leave. Any accumulated and unused annual leave in excess of 75 days or 600 hours shall be forfeited at the beginning of the first full pay period of the next calendar year. If an employee is denied the opportunity in 1 calendar year to use annual leave days in excess of the 75 days or 600 hours allowed to be carried over to the next year, the head of the employee’s principal unit may allow the employee compensation, at the employee’s regular rate of pay, for those excess leave days. The head of a principal unit may approve a request for compensation under this subsection only if: the appointing authority documents the unusual administrative reasons for having denied the employee the use of annual leave; and funds are available for that purpose.