Commission types and rates
Default commission rates are set at the category level. The "rate" consists of two components: "commission type" and "commission value". These two values work together to calculate the commission that sales reps receive for selling a particular item or service.
Commission rate structures are set in the General section of the category detail screen. See sample below. 
Commission Types and their Commission Values
The Comm Type is a drop-down list from which you select the type of commission structure you want. The Comm Val field holds the value that works with the Comm Type when calculating the final default commission. There are three choices for Comm Type.
Fixed Amount
This selection sets the Comm Value as-is. For example, selecting a Comm Type of Fixed Amount and entering a Comm Value of 10.00 will set a default commission to 10.00 per unit sold. The default amount will not change unless you change it manually.
% of Price
This selection will calculate the commission amount by multiplying the Comm Value by the selling price. If prices change–including price changes at the order level if users have that ability–the payout will adjust automatically.
% of Margin
This selection will calculate the commission amount by multiplying the Comm Value by the category's gross profit margin. If pricing changes, the payout will adjust automatically.