I am not a tax professional, but I am experienced with many aspects of taxes.

It sounds like you are using Form 1040A. 

Line 14a should contain the total Social security benefits for you and your spouse (if spouse is applicable).  This amount should match the sum of the amounts on Form SSA-1099, box 5, for you and your spouse.

Line 14b is the taxable portion of the amount on line 14a.  The amount on line 14b is usually less than or equal to the amount on line 14a.  This because for many people, not all of their social security benefits are taxable.  TurboTax calculates the taxable amount and places it in line 14b.

If you want more information, you can look at the IRS instructions for Form 1040A for these lines (on pages 29 - 31).  See https://www.irs.gov/pub/irs-pdf/i1040a.pdf

My calculations using the Social Security Benefits Worksheet (IRS.gov) did not match those of Turbotax for box 14b either.

Icbonazza: You did not say exactly which site you used, so I'm guessing that you may have used the wrong form or the wrong numbers in the correct form. The form I mentioned above, https://www.irs.gov/pub/irs-pdf/i1040a.pdf has a disclaimer regarding who is eligible to use it. Make certain that you are using the correct form, and double check all the numbers you used. Also, be sure to read the "Before You Begin" instructions at the top of page 30. (I would trust TurboTax.) The above form has the following exception on page 29: Exception. Don't use the Social Security Benefits Worksheet if any of the following applies. You made contributions to a traditional IRA for 2016 and you or your spouse were covered by a retirement plan at work. Instead, use the worksheets in Pub. 590-A to see if any of your social security benefits are taxable and to figure your IRA deduction.

I also suggest referring to the answers, especially VolvoGirl's answer, to:
  <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/3777695-on-the-back-of-the-ssa-1099-there-is-a-worksheet-to-deduct...>

You did not specify exactly which form you used.
If you used the form mentioned above, <a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/i1040a.pdf">https://www.irs.gov/pub/irs-pdf/i1040a.pdf</a>, be sure to read the exception on page 29, and the "Before You Begin" instructions on the top of page 30.