A consecutive series of data points over a high limit (or under a low limit) is deemed as an alarm event.
For example, in image below, there are 3 temperature high limit violation events for high alarm zone.
Error codes usually could be found on the upper left corner of a PDF report created by data logger, if you find an error code in a data report, it means data logger detected an exception during recording.
Code 0004 (*0004), logger used to be reset during recording, which may cause missing of data point.
Code 0005 (*0005), an internal time error is detected when activating a logger, to avoid creating incorrect data record, logger would not be activated in this case until new configuration is effective.