If it really has 8 and not 8.1. You will be able to update it for free to 8.1. After that, you can get 10 for free
I don't believe that you can upgrade directly from 8 to 10 but I could be wrong on that. Whatever the situation though, you will get 10 for free.
That being said, I doubt that there is a store that actually sells a laptop with 8 today. Probably they counted 8.1 as 8 or they didn't want to change the packaging