They are probably doing it game by game. I wouldn't worry about it. I have a partial refund at the moment too.
Makes up for my careless purchase of Monkeyball Adventure, which turns out not to be Vita compatible.
Big thanks to the people who took the time to do these refunds!!
The message to affected users should have gone out to everyone. Please check your XMB Messages to ensure you've received the following message:
Thank you for your recent purchase from the PlayStation Store. As you may have realized, we experienced some issues while processing transactions that resulted in a small number of users being charged for content that was listed as free. Unfortunately, you were one of the affected users and we are contacting you to let you know we are aware of the error and will be refunding the amount erroneously charged to your wallet. You should see the credit in your wallet by 2/21/13. Note that this will not affect the content you downloaded - the content is yours to keep. We are also including a voucher code, below, worth $5 to make up for any inconvenience
Vouchers must be redeemed into your account by May 31, 2013.