A timed section can be paused. The screen blanks so nothing can be read while the clock is held, and there is a cap on how long a pause can run.
The clock is authoritative on the server, and the page re-syncs to it. This matters: a browser tab in the background is throttled by the operating system and a sleeping device stops counting altogether, so a timer that lived only in the page could drift badly. If you have ever seen a clock jump, that is the failure it now prevents.
If a timer still looks wrong, report it through the Help button with the exam name and roughly when it happened.
Did this answer it? If not, the Help button in the bottom-right corner of any page reaches a person, signed in or not.