the most likely explanation is that you reported unemployment compensation and/or repayment of Obamacare excess premium credits and filed before TurboTax could be updated. if your Modified Adjusted Gross income is $150,000 or less the first $10,200 in unemployment compensation is no longer taxable and some states have also adopted that provision. the new law also eliminates repayment of excess Obamacare premiums received.
why are you amending? The IRS does not want amended returns filed by taxpayers that are trying to amend only for either or both of the reasons cited.