“Leave of absence” also means time during which a state member is excused from the performance of a portion of his or her duties and did not, during the absence, receive full compensation if the partial leave of absence was formally granted by the employer for one of the purposes specified in this article. The contributions and interest required of the member shall be determined by the section that defines the purpose of the leave and by the amount of service credit the member would have received had he or she not been absent.