A district's cost of education index adjustment for the 1997-1998 and 1998-1999 school years shall be computed by the commissioner of education by calculating each district's cost adjustment in §203.10 of this title (relating to Calculation of Adjustment for Cost Variations). If a school district has more than 1,600 students but not more than 2,000 students in average daily attendance (ADA), the commissioner shall modify the cost adjustment in §203.10 by multiplying it by the following size factor: 1.0 + ((2000 - ADA) * .00014).