When a client uses a gift card and another payment method to pay for an order, the refund process works as follows:
Example:
Order total: 100 EUR
Paid with gift card: 50 EUR
Paid with other payment method: 50 EUR
Returned items total: 60 EUR
Refund Process:
Shopify will regenerate a 50 EUR gift card, first. The remaining 10 EUR will be refunded to the original payment method (e.g. credit card).
Customers might expect a 50 EUR refund to their original payment method and a new 10 EUR gift card, but Shopify defaults to the process described above.