The incorrect piece of information is: "The spot marked 'maximum gravitational potential energy' should be on the lowest point of the roller coaster, at the far left side on the bottom."
This statement is incorrect because gravitational potential energy is highest at the highest points of the roller coaster, where the elevation is greatest. At the lowest point of the roller coaster, the gravitational potential energy is at its minimum, and the kinetic energy is at its maximum due to the conversion of potential energy to kinetic energy as the coaster descends.