Possible error in the question_answering notebook ?

[Sam131112]

In the question answering notebook after the cell max_answer_length = 30 this the next cell code

.......
start_indexes` = np.argsort(start_logits)[-1 : -n_best_size - 1 : -1].tolist()`
end_indexes = np.argsort(end_logits)[-1 : -n_best_size - 1 : -1].tolist()`
valid_answers = []`
for start_index in start_indexes:
    for end_index in end_indexes:
        # Don't consider out-of-scope answers, either because the indices are out of bounds or correspond
        # to part of the input_ids that are not in the context.
        if (
            start_index >= len(offset_mapping)
            or end_index >= len(offset_mapping)
            or offset_mapping[start_index] is None
            or offset_mapping[end_index] is None
        ):
  
            continue
........

Here start_indexes can never be more than sequence length becasue the argmax is over an array of 384 sequences i.e the max sequence length . So how does start_index >= len(offset_mapping) & end_index >= len(offset_mapping) make sense here ?