If you receive an early distribution from a 401K, then Box 7 of your 1099-R should show a Distribution Code of 1 or 2.
This is how the IRS (and TurboTax) know that the distribution was early.
See page 15 of this IRS Publication:
https://www.irs.gov/pub/irs-pdf/i1099r.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
