Incase admin wants to levy additional tax upon commission earnings he can easily do the same using these settings. 
So, let’s take for example if you want to tax a vendor 10% of the commission amount, you can easily do that as shown below
Thus here’s how the order distribution stands:
Product Cost: Rs 1000
Commission set ( percentage wise):10%
Vendor Earning: Rs 900
Commission Tax : 10% ( set)
Vendor Final earning: 900 – (900*10%)= Rs 810 ( as shown above)