according to the number of module credits

For Blackboard exams, there will be a 24 hour window within which you will have a fixed time to complete the exam. The fixed time will vary according to the number of module credits – four hours for a 15-credit module, six hours for a 30-credit module. You may start the exam at any time within the window but you must complete the exam within the 24 hour window (do not start the exam at 11:55 on the second day!). The exam will be set up so that if you experience brief internet or computer problems, you can re-enter the exam within the four or six hour window.