I have some funds in my wallet, and I have a couple of credit certificates that I have not deposited yet into my wallet for flexibility. Is there any way to use my wallet funds and use a credit certificate for the balance for my purchase? It seems like in the payment choices, I can only choose wallet funds OR credit certificates, but not both? If I add my credit certificates to my wallet, does it just pool all the value together so that would be a way to give me access to all the funds in total for my purchases?