Combined and weighted COT is put together by adding each of the below together......

S&P 500 at face value and served as the base point at $250 a contract

S&P 500 mini divided by 5 since it is a $50 contract

NDX divided by 2.5 since it is a $100 contract

NDX mini divided by 12.5 since it is a $20 contract

Dow divided by 25 because it is only a 10 dollar contract

DOW mini divided by 50 because it is a $5 contract

Russell 2000 is multiplied by 2 because it is a $500 contract

Russell 2000 mini is divided by 2.5 because it is a $100 contract

S&P 400 is multiplied by 2 because it is a $500 contract

S&P 400 mini is divided by 2.5 because it is a $100 contract

From

http://www.cftc.gov/dea/newcot/deafut.txt