(a) Any member having accumulated and unused sick leave at date of retirement shall be entitled to service credit towards the service retirement annuity to which the member may be entitled. The credit for accumulated and unused sick leave shall be 1 month for any period of 11 to 20 days inclusive of such leave and ½ month for any period of 5 to 10 days inclusive except that the credit for accumulated and unused sick leave shall be one year for any period consisting of 2080 hours. Less than 5 days of such unused sick leave shall not be considered for such credit.
(b) If at the date of retirement a member is indebted to the Government for advanced or unearned sick leave, ten (10%) percent of the amount of each basic annuity payment shall be deducted until the member shall have reimbursed the Government in full for the value of such advanced sick leave at the rate of compensation received by the member immediately prior to his date of retirement.