Upon becoming a member of the retirement system to which a person has transferred, such member shall thereafter be entitled to the rights, benefits, and annuities as are provided in such retirement system; provided, however, anything to the contrary notwithstanding, that upon retirement the allowances and benefits shall be calculated as though the time which was served and credited while such person was a member of the retirement system from which he or she transferred shall be counted and credited as though such person had been a member of the retirement system to which he or she transferred during such period of time; provided, further, that the retirement system from which a transfer was made shall pay monthly to the other retirement system that portion of the monthly benefits attributed to the retired member's creditable service in the retirement system from which the member transferred, less any annuities or other benefits calculated at retirement and applicable to Teachers Insurance and Annuity Association or the federal civil service retirement system and less the state annuity and death benefits payable for prior service under §§ 8-3933 and 8-3937 for those members transferring from the University of Tennessee retirement system. In computing the respective obligations of the two (2) retirement systems, the member's creditable service in both retirement systems shall be combined, and the “average final compensation” shall be determined by the highest average earned in either or both retirement systems. Each retirement system's obligation for monthly benefits shall be the same percentage of the total monthly benefits as the percentage of creditable service in that particular retirement system is to the total combined creditable service of the member in both retirement systems.