If you want to inform something to your affiliate about the payout, then you add notes to the Invoice

Step 1. Click on "Rewards" on the Dashboard

Step 2. Under "Manage Invoices", click the blue "Edit" button across a specific Affiliate

Step 3. In the next page, scroll down to see the Comments Box. First box is for internal comments for the yourself(Admin). Second box is for the Affiliate to see.

Step 4. Add your notes and click "Update"