It's a very specific notion of "done" - you can record an offline authorization event; so the
customer-visible part is done, but the actual payment is not.
The merchant is not going to have any access to that money whatsoever until/unless connectivity is restored. They can't pay their suppliers or employees with that money while they're offline.
It's pretty much the digital equivalent of scribbling "Bob authorised to pay me $12.34" on a notebook that you're going to bring to the bank afterwards.