On every online order Storedoor collects for you, two amounts come off before the money becomes yours: the card fee and the platform commission.
You can see both in two places on the Payouts page. The Commissions tab gives you a line per order: the Amount of the order, then the Card Fee and the Commission in red, then Your Earnings in green. The Fee Summary card on the Overview tab adds them up for the life of your store, under Card Fees Paid and Platform Commission.
When you refund an order, a Refund line joins the Commissions tab. The commission on it shows in green, because it comes back to you, and the Card Fee column reads Not refundable.