Yes, the top and bottom can be adjusted separately but it also allows you to take the door off and maintain the horizontal adjustment.
The big part is inserted into the square door hinge bobbin. There is a washer on the outside and inside of the door and a large nut that locks it in the horizontal adjustment. There are flats on the bottom to aid in holding it so you can tighten it's nut. The smaller threaded part has a 'nose' with a shoulder at one end and a square wrenching part on the other end. The 'nose' goes into the bobbin in the door jamb and the shoulder is what allows you to make vertical adjustments. The nut on this part is what locks it vertically.
You might want to make a wrench out of some flat steel stock to grab the flats on the big piece. The jaws of that wrench should be about an inch. Be sure to wrap tape around it so you don't scarf up your paint. A 1 1/4" deep socket is very useful for tightening the big nut. I don't remember what size the little nut is but the deep socket will go over it. The square wrenching flats on the end of the small part is 7/16" I think.
When adjusting the height, obviously you have to adjust both hinges - so to move the door up, you want to screw the small inner piece in or down (extend it out the bottom of the door) on the bottom hinge and screw it out or down (screw it into the door. Adjusting the horizontal dimension is pretty straight forward.
The only tip I can suggest is to try to prop up the door with a floor jack or similar to where you think it ought to go, tighten up the nuts and test it. I spent hours on my passenger door so the lock would work. I'm still not satisfied with it but it is workable. I still need to revisit the complete adjustment as both doors let too much rain in.
Of course, if your doors are good horizontally, then you just have to adjust the inner small pieces to raise it or lower it.
Let me know if any of that is not clear.
Good luck!
