See this TurboTax support FAQ for amending a tax return (2018 thru 2016) - https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-filed/01/25588
Line six i would like to change from -1 to zero
On capital gains or loss I want to change it from -1 to 0