It isn't, you're probably misreading the error message and that's what your function wrongly returned, not the expected value:

expected        [ 9, +0, 9, 1, 2, 1, 1, 3, 1, 9, +0, +0, 9, +0, +0, +0, +0, +0, +0, +0 ] // this is your answer
to deeply equal [ 9, 9, 1, 2, 1, 1, 3, 1, 9, 9, +0, +0, +0, +0, +0, +0, +0, +0, +0, +0 ] // this is the expected result

JavaScript Completions 55050