Line 18, column e refers to the Exercise Price of your stock. That information can be found on Form 3921 which you should have received from your employer.
To edit the amount in TurboTax, you will need to edit your entry. Go back to the Investments section (type 1099-b into the search bar and use the Jump to 1099-b link), and click on Edit (pencil icon) next to that sale.
Check the box that says The cost basis is incorrect or missing on my 1099-B. Then Continue. You will get a few questions about your employer and whether or not the associated W-2 is included on this tax return.
Then you will get to the questions about the From 3921. You can enter the information with or without the document, but it is better if you have it. You can update the exercise price (box 3) from the Let's get some purchase (exercise) info about this sale! screen. The Employee Stock Transaction Worksheet will be updated to reflect what you entered.
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