There are potentially two time dials on a learning module in test mode, and they need to work in unison least one stomp on the other.
1) The due date of the assignment (on the specific assignment's 'edit settings' page) is when all students will loose access to the assignment (unless they have a late submit, or the specified time allotted for the test has been used). This is why SSD students may have (1.5x, 2x) extra time granted but still be stopped short (without a late submit); more info on how to help these systems agree here.
2) The 'time limit' is a feature only offered on learning modules which sets an (optional) timer within the larger start and due date window in which students must complete the assignment. In the examples below, students are provided 20 minutes within a larger 2 hour start/due date window. If a student starts with less than 20 minutes before the due date, their timer will be adjusted to reflect the amount of remaining time before the due date cut off.
(current)
(coming Spring 2021)
This 'time limit' is what ADA/SSD students time is multiplied by. It is also reflected in the exam dashboard of a test and can be adjusted should their be technical difficulties or reason to add additional time to an individual or class full of students. While the exam dashboard offers a one stop centralized place to monitor students as they are taking their exam, in this case just know you can add time using the indicated 'add time/add' for an individual student, or 'add time to ALL students/update' drop downs.