Issue: ArchFX React shows a negative "units lost" value.
Root cause: The line is running ahead of schedule (faster than the target takt time), so the "time lost" is negative and accordingly the "units lost" is negative as well.
Workaround: Decrease target takt time. If you find that a job is regularly showing negative time lost and units lost on a particular line, this suggests that the target takt time is too long. Shortening the target takt time will reduce the frequency that the line is running "ahead of schedule."