If they keep Reddit as part of the mothership they can't sell it whole or in part. This is the first step in a process of divestment. The valuation that they are tossing around should be seen as the asking price if and when they do. It would highly surprise me if that asking price was met or even approached by an outside party.

Note that a deal at that valuation did not go through, and that likely that valuation was an important reason why it didn't.