Quiz final scoring issues

Hi everyone,

I have an issue with the final scoring of a quiz that I have made and that uses a questions bank. I use Articulate 2.

The quiz is pretty straightforward : The first screen is the title, then the user has to answer 30 questions that are drawn from a question bank of 62 questions, and finally a last slide shows the result.

I have the follwing problem : If the learner quits the quiz, after, let's say, 20 questions, and opens it again to answer the last 10 questions, the final score is calculated based on these 10 questions, and not on the whole 30 questions. That means that if I had answer correctly to all the 30 questions, I will only have a 33.33% final score.

I don't know how to solve this problem. Your help would be much welcomed.

Many thanks