Total gross commission (TGC) - is a gross commission earned by both buying side and listing side, combined. However, many brokerages only input the gross commission of the side(s) they are representing.
To be able to adjust the total gross commission please navigate to the "Commissions" tab and click the "0" link from the top of the screen. Once a pop-up window occurs you will be able to change it.
The video below shows different ways on how to change gross commission.