what does this mean

c_helper.py:148: in _t
    self.assertEqual(stdout, expected_stdout)
E   AssertionError: '16416123456733' != '1\n6\n4161234567\n3'
E   - 16416123456733
E   ?             ^
E   + 1
E   6
E   4161234567
E   3
E   ?  + +          ^