Assuming it was for a state tax refund, if you did not used itemized deductions on your 2016 tax return then you can disregard the document.
However, if you did itemize deductions then the state tax refund will be a taxable item on your tax return. I would suggest that you amend the return because if you wait for the IRS to match it to your return it could be as long as two years down the road which would accumulate penalties and interest on the balance due because of it.
There is no rush, you have until April 17th to amend the return and you don't want to do it until your return has been fully processed. When the amended return is ready (approximately another week or so), you can always try it to see if it makes any difference on your tax return. If you don't owe any money on an amendment, you don't have to file it.
The instructions to amend are included below, you can keep checking back to see when it's available, but not before your return is accepted by the IRS and processed.
https://ttlc.intuit.com/replies/3288565
