This is a wave traveling at constant speed. The pulse moves 1.0 m to the right every second.
The leading edge of the wave is 1.0 m from x = 6.0 m. Because it is travelling at 1.0 m/s, it will take 1.0 s for the leading edge to reach x = 6 m. thus the history graph for x = 6 m is will be zero until t = 1.0 s.
The first part of the wave causes a positive displacement of the medium so immediately after t = 1.0 s the displacement at x = 6 remains positive. This portion of the wave is 4 m wide and takes 4.0 s to pass x = 6 m.
The trailing edge of the pulse arrives at t = 5.0 s. The displacement at x = 6 returns to zero at t = 6.0 s and remains zeor for all later times.