The graph shows the spacecraft speed wrt the Sun during the DSM-2 and the resulting acceleration.
The change in the velocity vector was 16.9 m/s, while the change in the magnitude of the heliocentric velocity was 2.54 m/s.
October 2018: Asteroid Approach Maneuvers 1-3
The following three graphs show the first three Asteroid Approach Maneuvers designed to slow the spacecraft speed relative to Bennu.