New users count much bigger than actual sales on iOS

Unity analytics number for new users (for the last two days) is much bigger than actual sales in iTunes. Why is that?

Hi @DavidGrof
There is one thing I want to clarify is how we count a new user.
The first time your app is launched a unique user ID is created and stored locally on the device. This user ID is how we distinguish users from one another. Since the id is stored locally on the device, if a user reinstalls or deletes the file that contains the user id, the next time the app is launched a new user id will be generated and they will be counted as a new user.

I notice this in my app. I think the actual reason for the diff is pirated apps. They will be counted by Unity Analytics but not by iTunes.