Erase macintosh HD data

Everything need to be erased and the OS reinstalled - follow all of the instructions here:

https://support.apple.com/en-us/HT201065

FWIW, the Data volume contains all of your user data and files.

Here’s what to do before you sell your Mac: What to do before you sell, give away, or trade in your Mac - Apple Support.

Choose “View” > “Show All Devices”.

Then, select APPLE HDD or APPLE SSD, and click erase. (If Fusion Drive is at the top, erase Container.)

Name: Macintosh HD

Format: APFS

Scheme (if shown): GUID

They need to do more than that before selling it.

That’s the link I posted.

Sorry. Your link didn’t have the text. It was an oversight on my part.

No problem - I don't bother when I'm on the iPad because it's a pain with the keyboard. Just didn't want the OP to become confused.