Zuora does not allow for a refund to be more than the actual payment that was done.
So if the customer paid $10.00, then you can only make a full refund of $10.00 or a partial refund i.e. $7.15 for instance.
I understand that your Payment Gateway Ingenico ePayments might have this feature available for their customers, but within Zuora's system, this is not possible.
If you are trying to provide Credit to a customer, please have a look at the following article and let me know if that helps.
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