Hello, I'm new to Shot Peening. In developing the Sieve Analysis procedure, I created an excel to calculate the percent pass. However my question is (rather 2):

1) Other than a visual - how does graphing the results help? To me it is either passing the percentage or not.
2) Per AMS2430U It seems I only need 2 sieves per table 1 pg 4, One that allows .5% to be retained on sieve and on that allows 20% to pass through, thus 80% retention in sieve.

So my question is :Is my interpretation correct and why in all my searches everyone is using 5 or more sieves?