It’s just checking to make sure file copy is REALLY complete.
Sometimes the little progress bar will go away, but files aren’t actually done. Or maybe you’ve got a document open that’s saved to the spreadsheet. Or a bunch of possible problems.
“Safely remove” is just a quick check. You’re *probably* safe to remove the Thumb Drive without doing the “Safe to Eject” thing. But if you want more than *probably*, eject it properly.
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