It is a new Frigidaire unit and the only specs I found on it were as follows: "All electric cooktops run off a single phase, 3-wire or 4-wire cable, 240/208volt, 60 hertz, AC only electrical supply with ground."
OK, so this is a straight 240v appliance. The 4-wire illustration is only there for installations where this unit is replacing a unit with a 4-wire feed.
For your new circuit you would use 10/2 or 8/2 cable. IMO for what you are installing 10/2 is fine. Especially considering the short distance and that this is brand new unit. Any future upgrade, while unlikely any time soon, will not be very hard.