When filing 1040X to correct cost basis on 1099B, do I enter the correct case basis, or do I enter the difference between the original and the correct cost basis?

E*Trade cost basis did not include an amount already taxed in my W2, so I need to amend. Figured out how to create the 1040X in TT, but unsure which number to report - the accurate cost basis, or the difference between the accurate number and the number in my original return. Also - cost basis is the only number I am including on 1040X, correct? Thank you!