TurboTax is using the correct amount. The rules for the standard deduction do not apply to the deduction for seniors.
IRC Section 151(d)(5)(C)(iii)(I) says "In the case of any taxpayer for any taxable year, the $6,000 amount in clause (i) shall be reduced (but not below zero) by 6 percent of so much of the taxpayer’s modified adjusted gross income as exceeds $75,000 ($150,000 in the case of a joint return)."
Filing as QSS is not a joint return.
The IRS instructions for Schedule 1-A Part V (on page 110 of the Instructions for Form 1040) say:
"The $6,000 per person amount is reduced if your MAGI is more than the amount shown next for your filing status.
• Married filing jointly—$150,000.
• Single, Head of household, or Qualifying surviving spouse—$75,000."
