It was the edited dictionary that was provided with the course and yes every 5th word was removed, it seems to make it fit. That info is posted on the forum. Thats why it's a dictionary without a tree in it.
RE American spelling... I use Australian spelling 
that's why I use the Macquarie Dictionary.
For the record the first 3 words I picked... the page number, column and postition correctly, so I'm glad the following words weren't in the book. I haven't bothered playing that game again since I've found other interesting mind games to play.
