It means your monitoring system is not real-time, and may be missing some inputs from time to time.
Calculations like "engine load" or "BMEP" are derivative from other measuremens, and usually short term averages, a snapshot of some segment of the recent past. There will also be lags from sensors to monitor, monitor to computer. There is interference from the operating system, "I'll get to dealing with that piece of information coming into the USB when I'm done doing what I'm doing now." When writing real-time software for process control, we could never work through general purpose operating systems, and certainly not the clunky multi-tasking system a laptop would have, which has to focus on user-interface inputs above all other information.
Tom Test
Itasca Spirit 29B