very difficult sumproduct formula. SO SO DIFFICULT!! HELP ME!!!!!

[amartino44]

Hello. I was given the formula below and asked if someone could explain what it was doing. I tried to use the evaluate formula but I didn't understand it. Could someone break it down piece by piece for me? Also, could someone adjust it so that it makes row 6 (starting in C6) equal to the values in row 50 in the attached spreadsheet. The formula does the right calculation (on row 5) but when I copied it from the example it doesn't work on the new sheet. Thanks.

=SUMPRODUCT(1-COLUMN($A3:INDEX($A3:A3,MIN(12,COLUMN(A3))))*8.3333%,N(OFFSET($A2,,COLUMNS($A3:A3)-COLUMN($A3:INDEX($A3:A3,MIN(12,COLUMN(A3)))))))