Any annuitant who is receiving a retirement annuity of less than $7,500 annually on the effective date of this section shall receive a supplemental benefit, prospectively, under this section: Provided, That the effective date of retirement for such annuitant was prior to July 1, 1979, and he had ten years or more of credited service at the time of such retirement. For the purposes of this section, "effective date of retirement" means the last day of actual employment, or the last day carried on the payroll of the employer, whichever is later, together with a meeting fully of all eligibility requirements for retirement prior to the aforesaid effective date. Any annuitant retired pursuant to the disability provisions of this article shall be considered to have had ten years or more credited service at the time of such retirement.

Each such annuitant shall receive as his supplemental benefit an increased annual amount which is the product of the sum of $18 multiplied by his years of credited service: Provided, That the total annuity of any annuitant affected by the provisions of this section, together with any of the other provisions of this article, shall not exceed $7,500 annually.

Any annuitant receiving the supplemental benefit provided for herein for the annuity payment period just prior to July 1, 1985, or any annuitant made newly eligible for receipt of such supplemental benefit on such date, shall receive a nineteen percent increase in the amount of such supplemental benefit prior received or newly calculated, effective on and after July 1, 1985, and irrespective of the maximum total annuity proviso, and limitation of $7,500 annually. In any fiscal year in which pay increases are granted by the Legislature to active teachers, there may also be given an increase in retirement benefits for retired teachers, if funding is available for this purpose.

For the purpose of calculating the supplemental benefit provided in this section, fractional parts of a service credit year are to be disregarded unless in excess of one half of a credited service year, in which event the same shall constitute a full year of service credit.

On or after July 1, 1982, for the purpose of computation for determination of eligibility and for the amount of any supplemental benefit hereunder, separate computation shall be made of a retirant's own benefit and that which may be receivable as beneficiary of another, under the provisions of this article, with each such benefit being eligible for the supplemental benefit herein provided.