As I understand it, you had payroll deductions for your FSA removed from payroll in 2017, but the FSA did not pay those child care expenses until early 2018, right?
If so, you need to ask your employer if their FSA plan contains a "grace period", that is, if the plan allows for some or all of the FSA funds collected in 2017 to be carried over to the first three months of 2018 and spent then.
If so, you recall the "unusual" situations I mentioned above near the end of the interview? Yep, this is one of them. Check the box "We paid 2018 expenses using excess contributions that were carried over from 2017." and on the next screen, you will be asked for the amount of the carryover.
If, on the other hand, your FSA doesn't give you the ability to carry over any FSA funds, then you will have to check the other situation ("In 2018, we paid for 2017 care expenses that weren't reported in 2017"), and probably have to use IRS Pub 503 (https://www.irs.gov/publications/p503#en_US_2018_publink[phone number removed]) to calculate the amount to enter (TurboTax will tell you where to go).
Then you should have a heart-to-heart chat with your HR people to encourage then to get your W-2 right the first time, and the FSA expenses paid in the proper year.
