This app was mentioned in
with an average of
Because those are NEW apps .
Also numbers on store are changing like this 10,50,100,500,1000,5000,10 000,50 000...
And I don't see problem with showing new apps on top. One of the biggest problem with store is fact that top apps never change, new apps has no chance to be seen. Even some old apps that are not updated for years are on top because of downloads.
Example [link] , this app is on 4 place(in my country, in US is 10) top free comic apps,last update was more than 3 years ago. Play Store ranking system sucks and is good to see new apps on top. Unfortunately those new apps will be removed from new and you will never see most of them unless they have huge marketing campaign and get 100 000 or more downloads.