In the guessnumber-jsf example, as described by chapter 8.3, the described functionality is that Duke will pick a random number between 0 and 10, while the implementation will give a random number between 0 and 9.
Changing code line
randomInt = new Integer(randomGR.nextInt(10));
randomInt = new Integer(randomGR.nextInt(11));
would make the implementation match the description.
It is a minor issue that has no effect on what the example intends to demonstrate, but still might want to have it aligned.