When a service is triggered by a timer and the service is still running, list-timers shows "x ago" for LEFT, x being the same value as PASSED. I would expect LEFT to show the next invocation instead, or even better, indicate that the service is currently running (maybe by simply writing "running" instead of the time).
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.