Unfortunately, the short answer is that it depends. Different exams and different subjects take different amounts of time. Also, there is not an exact amount of time for each test, but rather a minimum and maximum amount of time for each test section.
A student may not be excused from a test session until all students in their exam room have completed the test. Additionally, it takes time to sign students in, get them seated, set up their computer, etc. Your site coordinator can give you more specific guidance on about how long your student’s testing will take each day.