Quiz results/score are over 100 points
Thanks everyone for your answer. Finally, I've achived to solve the problem. At first, this bug comes from last versions. 

If you create in this module a Long Question which max score is 0, it creates an inconsistency because you cannot divide by 0.

Some months ago, I found a patch to solve it:

https://www.drupal.org/node/2394759

But it's incomplete, because the module save the scores of each question in database and then it updates the total score adding the score of each one.

So, the way to solve that is changing the next lines in the same file that the patch file (../question_types/long_answer/long_answer.module):

db_update('quiz_node_results_answer')
  -&gt;fields(array(
     'points_awarded' =&gt; $points_awarded,
     'is_correct' =&gt; $is_correct,
))


to

db_update('quiz_node_results_answer')
  -&gt;fields(array(
     'points_awarded' =&gt; $calculated_score,
     'is_correct' =&gt; $is_correct,
))


To note the change is the variable $points_awarded for the variable calculated in the patch: $calculated_score.

With these changes, the patch is complete and everything is working.