The devices that are listed as in Grade A or 9/10 condition will have minor use signs, there should only be a little bit of scratches on the phone and most likely will not be on the screen.
Grade B or 7/10
The devices that are listed as in Grade B or 7/10 condition will have some use signs that include scratches (can be on screen), small dents on the corners.
Grade C or 5/10
The devices that are listed as in Grade C or 5/10 condition will have heavy use signs, a lot of scratches and dents but there will never be a crack.