We're happy that you're asking for the "displacement", because displacement is simply the straight-line distance between the start-point and end-point, and we don't care about any of the motions or gyrations along the way.
From the graph:
-- The location of the object at time-zero, when time begins, is 10 meters.
-- The location of the object after 6.0 seconds is 4 meters.
-- The distance between the start-point and end-point is
(final location) - (initial location)
-- So Displacement = (4 meters) - (10 meters)
Displacement = -6 meters