You started YPN on November 18 and you have a number above zero in your available balance?
From what I understand, Available Balance are those earnings that have passed the Net 30 day wait limit so that they are finalized. This is money that you can transfer to your Yahoo Search Marketing advertiser account (if you have one), or that will be payable once the time they cut checks arrives (if your Available Balance is over $100).
If you started on November 18, it doesn't make sense that you would have any amount in your Available Balance because you wouldn't have any earnings that are 30 days old yet.
The definition of Total Balance can be found if you hover your mouse over the blue question mark next to the words "Account Balance" right above those figures.