You have to enter the full amount that's on the 1099-MISC, even if it's wrong. If you don't, the IRS computers will pick it up as underreporting, and you will get an IRS notice saying that your tax return is wrong. The IRS doesn't see the individual income lines that you enter in TurboTax. They only see the total. That's why I suggest entering the correction as a business expense. Critter-3 is suggesting the same thing. Follow her instructions for where to enter it.
However, if you are reporting other self-employment income that was not reported on a 1099-MISC, you could subtract the correction from that income. The important thing is that the gross income on Schedule C (line 1) is at least as much as the total of all the 1099-MISC forms you received. As long as that's true, you won't attract the IRS's attention.
