http://processing.org/reference/sort_.html

> s = sort(s, 3);
> println(s);  // Prints bear, dear, elephant on separate lines

Above suggests, that s.length == 3, while before sort it was 5.

> For example if there are 12 elements in an array and if count is the
> value 5, only the first five elements on the array will be sorted

And this suggests, that s.length == 12 (doesn't change), but only the first 5 elements will be sorted.

From what I found out, the second definition is correct, so the example should say:

> s = sort(s, 3);
> println(s);  // Prints bear, dear, elephant, aardvark, cat on separate lines