Both the mini-exams and the full length practice tests give warnings about the time it will take before you start the section.
Pay attention to the time quoted before you start!
Once you enter the section you will be given further warnings:
Read this page carefully. Notice that both types of exams give you warning about the amount of time (1) you have to complete the exam and warnings that you cannot go back. Also, note the Practice exams state you can take breaks between the sections (2). There is a final warning that you cannot pause or retake the section later (3). Consider these warnings before starting the timer (4).