The App Store is somewhat shrouded in mystery, thanks a secret recipe that Apple uses to determine what apps shoot up the charts. Downloads play a big, influential role, but they aren’t the only factor. That being said, Readdle, developer of Calendars 5, Scanner Pro and many other apps, shared some data with us on Tuesday that could help other devs get an indication of what download numbers might lead to top ranking. Readdle’s Denys Zhadanov says that the company has found it takes between 3,500 and 3,800 downloads per day of a 4.5 star ranked app to break into the Top 10 U.S. Paid iPhone app list on Apple’s mobile software marketplace. That’s based on their experience with Scanner Pro, a universal app which recently cracked the top 10, and Calendars 5, their revamped calendar application recently released for iPhone. This echoes a study released by app research firm Distimo back in June.