This version of ZoneMinder records detailed information about events in the Stats table. This can help in profiling what the optimum settings are for Zones though this is tricky at present. However in future releases this will be done more easily and intuitively, especially with a large sample of events. The default option of 'yes' allows this information to be collected now in readiness for this but if you are concerned about performance you can switch this off in which case no Stats information will be saved.