How do I answer this question confirm or enter the amount of the Social Security/Railroad Retirement benefits that is not subject to

Seems like your question was cut off----what is the rest of your question?

What is the rest of the question?  Where is it asking you this?  

I think you are trying to determine the amount of your social security benefits that are not subject to federal income tax. If so, it would be the amount listed on line 6 of your Form 1040 (social security benefits) less the amount listed on line 6(b) (taxable social security benefits). 

To view your form 1040 and schedule 1 to 3:

1. Choose Tax Tools from your left menu bar in TurboTax Online
2. Choose Tools
3. Choose View Tax Summary
4. See the Preview my 1040 option in the left menu bar and click on it
5. Choose the Back option in the left menu bar when you are done