While Jetti can automatically calculate the commission, shipping and landed costs, you can want to occasionally manually add or subtract an amount from an invoice. For example, to add a one-off shipping charge. Or, refund for an item.
This can be done from within the payment report for the vendor. You'll first need to locate the invoice. It may not be showing by default, so you may need to adjust the date range or click to view all orders within a returns period.
Once the invoice is found, click on the adjustments column. Adding a positive amount will increase the payout (i.e. the vendor will receive more money).