OUTPUT DISTINCT SUM AMOUNT VALUES

Since I don't know the structure of your report, I can give you a code alternative.
If you look at report properties code, you will see a number of pre-built functions. You can add one that accumulates your total whenever your group variable changes by keeping the old group variable value in your code and comparing it to the current.
You can also do the same thing in NAV and calculate and pass the sum amount using code.