[tst]

I think these numbers are based on one blog post the company made[1].

They wrote:

"[...] defined that an app has to hold a position for at least 7 days to be considered as "ranked". That was the case for 265,959 apps from the 18th of July 2012 to 25th of July 2012. To the remaining 410.023 apps off the ranks, we refer as app zombies, leading a life outside a prospering market."

and

"[...] in theory app zombies can still be downloaded, we concluded that an average zombie is getting zero to ten downloads a day, depending on the country."

[1]: http://www.apptrace.com/blog/2012-08-06/inside-zombie-land