I need to lower the vertical beam of my driver side headlight just a tad because I noticed its a little farther down the road at night and brighter/upward in the trunks of cars in front of me. Which hex screw do I turn to adjust the height?

Its the adjuster on the left for vertical and the one on the right for horizontal.

according to gm with your car 25 feet from a wall they should be 5 inches lower than the distance from the plastic dot on your head light to the ground.
ie if the aiming dot on the head light is 25" to the gound then at 25 feet the light should be at 20".....hope that makes sense?

You sure? Because the one on the left looks like it connects right to the inner portion of the headlight and it seems that if that was adjusted that it would push or pull the corner of the light...in other words, affect the horizantal beam.

But if your sure your sure. You sure?

This is for a 1998 Pontiac Bonneville

Place the vehicle on a level pad or surface.
Close the doors.
Ensure that the fuel level is at a 1/2 tank or less.
Ensure that the tires are inflated to the proper pressure.
Complete the following steps and refer to the accompanying illustrations in order to adjust the headlamp aim:

1) Ensure that the headlamps are a distance of 7.6 m (25 ft) away from the wall.

2) Mark a vertical line on the wall. Align the vertical line with the center line of the vehicle.
3) Mark a horizontal line on the wall. Ensure that the distance (3) of the line to the floor is equal to the distance from the center of the headlamp aim dot (2) to the floor.
4) Using the headlamp aim adjusters (1), ensure that the following specifications match the specifications in the illustrations.