The early service retirement allowance calculated under this part shall be computed as a service retirement allowance in accordance with part 2 of this chapter on the basis of the member's average final compensation and creditable service at the time of early service as follows:
Creditable Service Percent Reduced Benefit Due
at least 4 years 10%
at least 5 years 25%
at least 6 years 40%
at least 7 years 55%
at least 8 years 70%
at least 9 years 85%
at least 10 years 100%