It's a negative number, and it's red, instead of black like it usually is. It also says my bill was paid in full on the 27th of December (autopay), but there was nothing on my bank account reflecting that. What's up with that?
If your balance due is in the negatives that means that you have a credit balance (i.e. VZW owes you money), that will normally be deducted from your next bill. As for your bank not reflecting the payment yet, it can take a few days for VZW to actually pull if from your account, but they post payments on their side immediatley.