Inconsistent Output Size events verify that pages render the same output to the client each time. If pages do not render the same each time, some clients are seeing different output than others and an error has occurred.
Production environments use this event as an indicator for possible usability issues.
Inconsistent Output events generate an event whenever the output size is below or above the normally produced average output. The default values for this event type are set to 0. To generate events, configure these settings to a value that suits acceptable variance in percents from output to output of scripts.
Event definitions are based on relative values i.e. percentage. Relative values are set according to warm-up settings, default value of 500 requests. If necessary, modify the default value by changing the zend_monitor.warmup_requests directive in the 'zend.ini'.