After defeating the warlock you get to his chest with all his treasures. In order to open it you need a combination of 3 keys. Luckily you found them all on your way. Each key has a number on it.
When you reached reference 139, you are told to choose 3 of the keys you have found and add their numbers together. You turn to that reference to find out if you have the correct combination of keys.
SPOILER ALERT I have found - a golden key with the number 125 - a copper key with the number 66 - a bronze key with the number 9 - a key with the number 111 - a key with the number 111 - a key with the number 99
Adding the golden, copper and bronze key (125+66+9=200) is deadly, because all keys are wrong. Adding 111+111+99=321 opens the chest and brings you to the end of the book (I said "spoiler alert" ;-)
All the other key combinations bring you to references where it tells you how many keys you got right. It's kind of the Mastermind game, where you try a combination and you're told how many you got correct.
Ok. All that is fine.
But the book has a reference that brings you to the end of the book, and it doesn't seem to fit any of the key combinations. That's reference 192. It brings you to the same place as 321.
Is this a mistake? Did I miss any keys on my quests on the firetop mountain?