In any assessment, there will be some variation in scores over repeated tests, but bigger discrepancies could suggest test-taker behaviour or motivation is a factor. Users may be tired, distracted or there might be other external factors that influence their test performance, such as a loud environment.
It's also important to consider how much time has passed between tests and how many hours of study the user has completed.
If there are bigger discrepancies than expected in a test taker's scores, we would recommend a retest. They should attempt the test in a quiet environment where they have plenty of time available to complete it to the best of their ability.