The supervisory board shall refund to a participant or beneficiary terminated from benefits by section five of this article the contributions of the participant in the same manner and with the same interest as provided to those participants or beneficiaries otherwise eligible to withdraw the participant's contributions under the retirement plan, less the amount of any benefits which the participant or his or her beneficiaries have previously received: Provided, That a member of the Teachers' Defined Contribution Retirement System whose benefits have been terminated pursuant to section five of this article shall be refunded only his or her employee contributions and the earnings on those contributions; and any vested employer contributions shall remain in the Teachers' Defined Contribution Retirement System and be used to offset future employer contributions for each contributing employer: Provided, however, That any former member of the Teachers' Defined Contribution Retirement System who affirmatively elected to transfer to the State Teachers' Retirement System pursuant to article seven-d, chapter eighteen of this code and whose benefits have been terminated pursuant to section five of this article shall be refunded only his or her employee contributions and the earnings on those contributions; and any vested employer contributions from the Teachers' Defined Contribution Retirement System shall remain in the State Teachers Retirement System to be used to offset future employer contributions for each contributing employer.