It's useless stats. My effective measure was turned off last year. Get turned on again somehow and I've tuned it off again now. Only one of the users that's counted as false growth where there is none.
It's completely off. Same applies to Alexa's guestimate of rank and traffic. We have never tried EM due to the privacy issues and 3rd party cookie dropping, but we did run an experiment with "Alexa certified metrics" and the stats were hugely off. Even Google Analytics underreported compared to web-server log analysis.
Many sites even have Google Analytics configured wrong and their tracking double accounts. Those EM stats are hardly representative of the real traffic in SA.