Each device in an ad hoc provisioning profile is identified by its unique device ID (UDID). The devices you register and add to a provisioning profile are stored in your developer account.

Each individual or organization can register up to 100 devices per product family per membership year for development and testing. You can register 100 devices of each type per year. For iOS apps, you can register 100 iPad, 100 iPhone, and 100 iPod Touch devices.

Apple distribute your pre release app for you using TestFlight then use iTunes Connect to invite testers. Optionally, distribute your app to 25 internal testers (your iTunes Connect users) or 1000 external testers per app (users with email addresses). Testers download and install thinned variants of your app using the TestFlight app available on the store.

To know more about app distribution use the link .