How do I get the extra $5 commision?

Could someone please advise on the following.

I have received a IMFPA from the seller but am needing some assistance as to the commisoin that was agreed between myself, and buyer. The seller will sell the commodity at $220 which is inclusive of commision. We negotiated with buyer a price of $225.  My question is this...How do i get the extra $5 commision?? Does the IMFPA need to be viewed and signed by, both the buyer and seller??? I am trying to overcome the buyer seeing my big commision. As the buyers price is not effected and he is getting the commodity for the price he agreed on $225. Should he care what commision i am getting for this???? In the IMFPA it reads like this...

TOTAL COMMISSION  OF    $4 USD    SHALL BE PAID BYSELLER  AS FOLLOWS:

The amount of delivered should be settled as herein stated to be transferred into the account as follows:

·         SELLER SIDE: $2 USD MT (CLOSED)

·         BUYER SIDE: $2 USD MT (OPEN)

can i adjust the buyer side commision to include the extra $5????????

Thank-you very much.