48 per aircraft.

"draws power from a docking station in the seatback and is normally viewed in that location."

So,  what did they do here? Equip the plane for 48 seat locations having  doc station power?..... OR  equip the plane with all seats having a doc station affording only 48 units ?

"confronts premium-only carriers"

 What is a premium only carrier? Shouldn't all seats offer the device?

doni