Obama: raising the debt ceiling doesn’t raise the debt

Can somebody help me understand this? How does raising the debt ceiling not raise our debt?

You may have heard this analogy before. You go home and see that your septic tank is backed up and sewage is filling up your house. You have 2 options: a) raise your ceiling to hold more sewage or b) stop the flow of sewage. Unfortunately, the rinocrat majority in congress keeps choosing option a.