Since you've adjusted the basis, leaving "Long-term basis reported to IRS (covered)" in the Sales section box on the Now, enter one sale on your [security] 1099‑B screen is fine.
You typically don't want to change what's on an information return such as a Form 1099-B. Adjustments to cost bases are fairly common, but changes to the category reported on a 1099-B, much less so. There's no reason to raise a red flag when you're doing everything correctly.
