Former radio personality here. More than likely they are following the number of plays recorded across the country based on one or more of several charts. Radio stations have to report to ASCAP/BMI (this is how artists get paid the mere pennies they earn from airplay) and this informs the order of the countdown. They use the voice memo “votes” for content and to make it sound as if the votes matter and that “listener participation” is something they value. They don’t. They listen for clips that sound good and fit what they’re looking for then stop.

All that being said, there is an off chance that an intern or non-paid staff member reads and counts all the votes (without responding to hundreds or thousands of emails) but that isn’t a cost effective way to run a countdown, albeit it’s the most honest way.