That adjustment is for the front camber using the special bolts.
FROM THE MANUAL
Check the rear axle camber. (POS+) = Positive Camber,
(NEG-) = Negative Camber. The camber on the rear axle is
not adjustable. If a substantial deviations in the rear axle
camber are found, the cause may be one of the following:
Refer to Page 2-13
.
Too great a difference in the vehicle level between the
right and left-hand sides of vehicle.
Camber strut bent.
Accident damage to the frame floor. Level differences
at the mounting points for the rear axle carrier between
the left and right sides of the body. Experience shows
that bending caused by an accident also has an effect on
the toe.