If you have paid back part of an unemployment benefit (an overpayment) do I put the amount paid to date or only what I had paid in 2016?

Enter only what you paid back in 2016.  According to the IRS regarding Repayment of Unemployment Benefits:

Deduct the repayment in the later year as an adjustment to gross income on Form 1040. (You can’t use Form 1040A or Form 1040EZ.) Include the repayment on Form 1040, line 36, and see the instructions there. If the amount you repay in a later year is more than $3,000, you may be able to take a credit against your tax for the later year instead of deducting the amount repaid. For more information on this, see Repayments .

For more information, see https://www.irs.gov/publications/p17/ch12.html#en_US_2016_publink1000172036