It has to do with how you answered the questions after you entered the form. Go back and edit the 1099-R. The distribution should be a mix of basis and earnings.
A qualified ROTH withdrawal has several requirements to be tax free:
All distributions from retirement accounts are classified as income. That just means that the distribution is required to be reported on your tax return. What matters is whether or not the distribution includes taxable income. For a nonqualified Roth IRA distribution, the taxable amount is determined on Form 8606. Qualified Roth IRA distributions are always nontaxable.