2nd HDD mising on new laptop?

I just bought a lenovo y50 and it says it has 1TB os storage but it says i only have 292GB. The guy who i bought it from said i have two HDD s one with about 250GB and another with 750GB and the second one isn t showing up.
Please help.
Thanks in advance.
Added (1). It said 1TB on the box
Added (2). The laptop is not used it's completely new. I bought it in a shop.

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