I agree it's unclear, unfortunately space constraints meant I couldn't figure out a good way to explain it better. Here's how it's supposed to work:
Pick the room you want to add details to.
If it's a 1, 2, or 3 look at it's highest neighbor. Check the table under [1][2][3] and use the detail that matches the highest neighboring die.
If it's a 4, 5, or 6 look at it's lowest neighbor. Check the table under [4][5][6] and use the detail that matches the lowest neighboring die.
So as an example, if you use the die layout that's on the card, the Throne Room (two 6s) has a 3 as it's lowest neighbor, so it's "Pristine".
Or the Jail die (the 1 near the rear) as a highest neighbor of 3, so it's "Trapped".