16. For each person responsible under section 11, the total of the credits and debits is calculated for each category of motor vehicles by determining the difference between the average emissions calculated pursuant to section 10 and the maximum standard applicable under section 6, 7 or 8, and by multiplying the result by the total number of vehicles taken into account in establishing the average emission value of the vehicles in the category. Credits and debits are expressed in grams of CO2 equivalent.