If you have already entered the individual sales you cannot just change the summary. You have to either correct the individual entries or delete all of the individual entries and make summary entries instead.
You used the word "amending." Did you already file your tax return, and you are now preparing an amended return (Form 1040-X), or are you still working on your tax return and making changes to information that you have entered in TurboTax but not filed?
Where exactly is the 1099-B summary that you want to change? Are you referring to a summary screen in TurboTax or something on the actual tax forms?
If you need more detailed help, please say whether you are using TurboTax Online or the CD/Download TurboTax software, and what edition (Basic, Deluxe, etc.).
