You can add accommodations for a student in New Quizzes. Accommodation settings include adding or removing time for all quiz attempts, and multiplying time limits by a set multiplier.
Accommodations apply to all quizzes in a course for a student and only one accommodation can be set per student. Set accommodations can be viewed in the Accommodations column and in the Moderate panel.
To manage timer settings for a single attempt, you can moderate a student's quiz attempt. Moderating a quiz attempt will apply any moderation settings on top of any set accommodations.
Note: Quiz availability dates still apply when moderating a quiz. If the Until date passes before a student completes an extra attempt or extended-time quiz, any in-progress quizzes auto-submit and the quiz closes, even if the student's attempt has not expired.