This is tricky. The IRS already adjusted your file, you don't need to amend to make the change they already made for you. It sounds like you should have gotten more money? In that case, you don't need to do anything unless you want your tax return to match what the IRS has on file.
If you think the adjustment is wrong, you have to start the amended return using the version already on file with the IRS, which includes the change they said they were making.
(Also, you filed by hand? turbotax would not have made that mistake.)
