Use the 4 adjusting screws of the optical plummet to adjust the remaining half of the deviation as shown below.
When the survey point is on the lower (upper) part of the illustration:
Loosen the upper (lower) adjusting screw slightly, and tighten the upper (lower) adjusting screw the same amount to move the survey point to a point directly under the center of the optical plummet. (It will move to the line in the figure on the right.)