An individual who, on June 30, 1987, is receiving benefits from the fund on an account paid under former chapter 15-39 is entitled to a monthly increase in that individual’s annuity. The monthly increase is fifteen dollars plus one dollar and fifty cents for every year benefits have been drawn from the fund, but cannot exceed an increase of seventy-five dollars per month. An individual who, on June 30, 1987, is receiving benefits from the fund on an account paid under this chapter is entitled to a monthly increase of one dollar and fifty cents for every year benefits have been drawn from the fund.