Full Refund You can refund the entire amount that you received in the payment.
Partial Refund You can refund part of the amount received in the payment. You can issue multiple, partial refunds as long as their sum does not exceed the captured amount.
A payment moves to the refunded state only when the entire amount is refunded to the customer. In case of partial refunds, the payment continues to remain in the captured state till the entire payment is refunded.