Hello Hans,
The inventory listing shows all the cards that you own, without splitting them by edition. This means that if you will add 1 Sylvan Library from Legends and then 1 Sylvan Library from 5th Edition, you will see 2 Sylvan Libraries, with a details icon near them. If you click it you will see the detailed view of your sylvan Libraries.
But still, they will be listed as 1 single item. When you hover on it, it cannot show more than one image (imagine entering a Mountain from all the editions it was printed in - what would you see then when you hover). So the image shown is, by convention - out of all possible card printings - the last printed image of that card.
The edition column that you see on the right shows the same thing. That is: the last edition and rarity this card was printed in. It is not a column indicating *all* editions you have of the card or all editions possible of that card, because that would make it a possibly very very big column .
I see this column is causing confusion, this has been mentioned before as a problem, and we will think on how to make it clear what it signifies. Also it is possible that we will add a second Expanded view of the inventory, for the collectors, where they would see instead of 2 Sylvan Libraries, a split view, like the one that is shown in the details dialog.