Periodically, processes that use ESF will report some statistics about the cache, such as how many entries are in use and what percentage of requests are fulfilled using the cache (the cache "utilization" or "hit rate"). The information is reported as an ESF message, so it will appear in the console log (for CAS processes) or the MFDS journal. By default, this happens about every hour, though processes will only report it when an ESF request is made, so idle processes (for example, SEPs that are never used) won't report.
You can configure how often this reporting happens by setting the report interval option. Its value is an integer, representing the approximate time between reports in seconds. Setting this to 0 disables reporting.