I assume the question is 'How does a $73K year become worth more than a $100K year?' If I misunderstand, then apologies for the following explanation.
The indexing factors for Earnings can be found here:
https://www.ssa.gov/OACT/COLA/awifactors.html
If you earned $73K in 2002, that is multiplied by an adjustment factor of 1.51. This goes into the average earnings calculation as $110K. If you earned $100K in 2014, that would be indexed by a factor of 1.08, or $108K in the average earnings calculation.
In my record, 1994 is my 3rd highest earning year, because of the indexing factors. What I earned in 1994 is multiplied by 2.12.
If I look at my 35th highest earning year, I find that it has an indexed value of $95342. If I were to work one more year, and max out the SS earnings, $132900, it would raise my career average monthly earnings by $89, and my monthly benefit at FRA would increase by $13 each month. (15% of the increase in Average monthly earnings).