This is a great question and something we are working to improve in terms of
removing the confusion. At any given time there are a certain subset of numbers currently used by robocallers. This number is generally around 30,000.
Each morning around 2am Eastern we update the apps to contain the 30K most recently identified active numbers. Then throughout the day we periodically add the new numbers which suddenly pop up as active, which increases the total numbers on your device as the day unfolds. By late evening some of those initial numbers have gone dormant so we build a new active database and push that out.
So basically it is a strategy to make sure your app has the very latest active numbers throughout the day.