Correct, it is an "above the line" deduction from your gross income, not a "below the line" tax credit. The net effect is that if you are in the 25% marginal tax bracket it reduced your tax liability by $5.

But only if you have enough other deductions that you itemize your tax return. Basically everyone gets a standard deduction (i.e., 5,800 if you are single). You can either take that, or you can deduct a list of qualified expenses (for most people, this is mortgage income, property tax, and state tax). If that puts you over the standard deduction, then you deduct this amount instead. Then you can start adding on things like charitable contributions. Otherwise, if you don't have enough deductions, and you take the standard one, then you can't add anything else to it. (Some exceptions apply, consult your tax professional for advice, the above is personal commentary only and not intended to be legal tax advice).