In the first example (see row 1), the word job is strongly associated to the word position, because the contexts of the latter in the examples 1 and 2 are similar to the context of the former, and not to the word task, whose contexts (4, 5 and 6) are radically different.
the second example (see row 2) of the word job is similar to the occurrences 4 and 5 of the word task, allowing its correct substitution.