Sounds like you got a deal. One square foot is a square that measures 12" X 12". A linear foot is a measurement of 12" in a straight line reguardless of width. If you purchased 12 feet(length) of carpet that is 12 feet wide you would have 144sq.ft....... or 12 linear feet(of 12ft. wide carpet)
At sq.ft price $7.98 X 144 = $1149.12
At linear ft price $10.64 X 12 = $127.68