Assigning different payouts to affiliates on the same offer is pretty easy, simply follow the steps below.
For a video version of this tutorial, please visit: [Video] Creating different payouts for affiliates.
Click Affiliates -> Affiliate Payout
Click Create to create a new affiliate payout
Select Offer: the offer that you want to set different payout
Select Affiliate: the affiliate that you want to have new payout for
Input on Current Payout: a different payout that you want to give the affiliate
Click Create to finish the process
That's it. You're done. A new payout is there.