Directly under the defintion of the hello world example is
"Here is the example explained"
..... You should start reading things in hex when working with binary files much more standard way of showing things.
That '0 and 11' is not a '0 and 11' it's 0x000B, It's a WORD (2 bytes, 16-bit integer) when when converted to decimal comes out to be 11. Which tells you the length of the next string "hello world" Count it, you'll see its true.
Same goes for anywhere else in the spec that states that it's a word.