Assignment Rule work item timeout is not correct is system time is not in sync.
For ex, if the work item timeout is set to 20 secs, the timer starts from 26 secs and ends at 6 secs.

Unlike for MacBook, the system time is synced with Apple Asia (time.asia.apple.com.) server.
For some customers, they have their own internal domain server.
Now sometime the link between the internal domain server and the user system is broken due to network issues, and the time does not get synced properly.
Because of which the user's system time is a few seconds/minutes behind, and that's the time when the AWA shows incorrect timer.

1. Set the assignment timeout as 20 secs in an assignment rule.
2. Impersonate as admin (end-user) and Fred Luddy (agent)
3. As end-user go to https://INSTANCE_NAME.service-now.com/sp and click on the VA bubble to connect to live agent.
4. Keep the system time out of sync (reduce the current time by 1 - 2 mins manually)
5. The work item countdown time shows an invalid wait time to accept the item.
6. Sync the time back and the work item now shows a correct timer.

Keep the system time in sync with the time servers used by Microsoft or Apple systems.
This issue mostly happens when you would use a domain server to sync the system time with.