Poshmark will issue you a shipping pass-through for however much you charged the buyer on an individual order basis. Once an order has been completed, we will add the shipping pass-through for that order directly into your redeemable balance.
You can see this in the "Shipping Pass-Through" column on your Sales Report.
You can also see this on an order level on your Redeemable Balance Activity Page: https://poshmark.com/account/redeemable_balance_activity.