Applicable exams you write may have a countdown timer detailing the time available you have to complete the exam. If the timer runs out before you have finished the exam, then the exam will be scored immediately.
You will no longer be able to answer any additional questions or change any previous questions for that exam attempt. If you leave your exam before you have completed it, the timer will continue for the full duration of the exam time limit.
It is advised that when you start an exam that has a time limit, that you do not navigate away from the page as you may lose time that can be spent attempting the exam.