The notice you received from the IRS should indicate what they changed on your filed tax return so that the taxable amount of your Social Security benefits increased. If you have questions concerning the IRS notice then call the number provided with the notice and speak with an IRS agent.
You can also get assistance in understanding the IRS notice you received from a TurboTax agent at the Audit Support Center. Use this website to access the Audit Support Center - https://support.turbotax.intuit.com/irs-notice/audit-support/
