The automatic calculation of estimated tax would include the capital gains that were on your 2018 return since TurboTax does not know that it was a one-time event.
Since you do have that knowledge, then it is permissible to disregard that income when calculating the estimated payments for 2019.
You can go through the section of your return described in the article below to create estimated payment vouchers based on your knowledge of your expected income for 2019.
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