It's your tax liability, not what you owe, so withholdings don't matter. There are tons of other threads outlining it, but for simplicity sake here's an example:
Assume you are single and have a gross income of 50,000. You automatically get the standard single deduction of $6,300 bringing the income to 43,700. Worse case you have zero other deductions your tax liability is calculated from this at $6,725.
But if you have a kid, a house, medical expenses or any other deductions, your taxable income would be reduced before the tax liability is calculated.