Each time you run the installation program, it creates a unique device name but offers you a check box (or something, it has been a while) to sign in under an already existing log in. A member log in can control many devices. And it is all right to reinstall on the same device, your statistics page will show a device name for 1 week after creation or 2 weeks after a result is returned, then the device name will age off your page. Your point score total will continue to show all your results.