Yes, please specify the amount you want to refund with the refund API.
example:
Cancellation after partial refund
It is not possible to cancel (Cancel a payment（DELETE: /v2/payments/{merchantPaymentId}）) after a partial refund has been made. Please note that if you request a cancellation, the request is accepted (code:REQUEST_ACCEPTED in the resultInfo), but the cancellation is not actually made.
If you want to cancel the refund of the remaining settlement amount after a partial refund
If you want to cancel the refund of the remaining settlement amount (settlement amount - partially refunded amount), please execute Refund a payment (POST: /v2/refunds)).
For more information on status transitions when refunding, please click here.