The number line representation is incorrect. (5 < x && x < 10) represents x has possible values of 6,7,8,9 (assuming x is int), whereas the number line shows that 5 and 10 are inclusive, but that's not the case as per the provided example.
Because all of the author's number line representations are consistent, I think you can consider them placing an implicit "open circle" on the bounds of all those ranges on the number line.
