The upgrade path for Apple devices (iPad and iPhone 4, 4S & 5) is from iOS 6.1.3/ 6.1.4 to 7.0. If the subscriber is on a software level below iOS 6.1.3 they will first have to upgrade to 6.1.3/4 then to iOS 7.0
The upgrade will be in the region of 700MB so that could be a hefty overall download, especially if people have multiple Apple devices.
The upgrade will be in the region of 700MB so that could be a hefty overall download, especially if people have multiple Apple devices.