how many devices you can have on your account
how many apple devices you can have on your apple account
Question marked as
According to: View and remove your associated devices for purchases - Apple Support
"You can have ten devices (no more than five computers) associated with your Apple ID for purchases at one time."
According to: Authorize or deauthorize your computer for iTunes Store purchases - Apple Support
"You can authorize up to 5 computers, which means that you can play your content on 5 different computers."