Yes that is correct. I usually buy the device package. My wife and myself switch between multiple devices. Android, Iphones, laptop, tablet etc. We just made sure that each of us only had one device connect at anyone time.
One time, we bought a three device package, because on our in-laws child needed internet access for school purposes. It was cheaper for her parents for us to have a third device. They paid us back with them buying me glasses of wine until we were even. Note. I didn't keep track if we were actually even.