If you are returning 5 or more items, your refund will be in the form of a gift certificate which can be used on future purchases. If you are returning less than an entire order (i.e. you purchased 25 pieces and are returning 20), then the quantity discount will be adjusted when calculating your refund.
Orders can be canceled at any time before they reach the Shipped status. Note, however that under current PayPal policy, PayPal no longer refunds the fees that sellers pay when a purchase is made through that platform. If you paid using PayPal, and subsequently cancel your order, the PayPal fees associated with your order (currently $0.30 + 2.9% of the total amount) will be withheld from your refund. This policy can be seen at the link below:
Under the section titled "Other Online Merchant Fees", it reads in part "If you refund (partially or fully) a transaction to a buyer or a donation to a donor, there are no fees to make the refund, but the fees you originally paid as the seller will not be returned to you." (emphasis added).