What does "balance" mean on the iTunes store? Is this money I owe, or money remaining on gift cards?

I have setup an iTunes account for my kid. We redeemed some gift cards on iTunes store. I don't have the account setup with a credit card because I don't want him to be able to buy things when the gift cards run out. I got an email saying that some songs were purchased with the amount they cost. Now I go to the iTunes store and login with my ID and it says my ID name, then "23.24". Do I owe that amount, or is that what's left on the gift cards?