Hi Samantha,

You may want to check out this article that explains how activity time is calculated for the coach reports: https://www.khanacademy.org/resources/k-12-teachers-1/modal/a/official-sat-practice-coach-tools-faq

If the students have another Khan Academy tab open in their browser, or if they have a spotty internet connection, it is possible that the time was not accurately counted.

If you're persistently experiencing problems with activity time not being logged, please report the problem via a support ticket so we can further investigate the issue.

Hope this helps! Please let me know if you have any further questions.