@LenaH ,
Thank you for your reply. I actually found my error via another post I submitted in the Education category, as I learned that Education is where several other posters submit questions on Form 8615. Please see here: https://ttlc.intuit.com/community/college-education/discussion/re-form-8615-line-9-instructions/01/3...
TurboTax calculated correctly; the error (as I was hoping) was mine. Via that other post, I now understand why TurboTax uses the Schedule D Tax Worksheet given my circumstances.
Thank you!
