Turbo tax says that I am entitled to a $464 refund. How is this possible since I have not paid in anything close to this amount?

"Refundable" tax credits.

Look at line 17 of form 1040.

Is this line 17 on the Federal return?

Yes, The most common credits are the Earned Income Credit and the Additional Child Tax Credit.

Some states also have "refundable" Credits. But they are less generous than the federal credits and it's unlikely that you would get a state refund if you didn't get a federal refund. You would have to identify your state for more help seeking out the source of a state refund.