E7470 Operating system disc

Hi 

I have just recieved my new Dell E7470, at some reason it is preinstalled with windows 7 pro, but the installation disc/recovery disc provided, is windows 10 pro, and there is a big white line accros the disc, that says "already installed on your computer". but since my computer is running windows 7 that is clearly not the case

What is the deal with that, and how do I get windows 10 Pro on my computer, i would use the provided dvd-rom, but there is no optical drive? 

PS why even provide dwd installation disc with a computer that does not have a optical drive?