Vacations and sick leave with pay as authorized in section 70A.1 shall only be taken at such times as the superintendent or the superintendent’s designee in charge of an officer or employee, as the case may be, may direct, and only after written authorization by the superintendent or the superintendent’s designee, and for the number of days specified in the authorization. A copy of the authorization shall be attached to the institution‘s copy of the payroll of the institution, for audit purposes, for the period during which the vacation was taken, and the semimonthly payroll shall show the number of days the person was absent under the authorization.