because there is a spring attached to the lever that adjusts the star
the top of the rear shoe will pull back in reverse only this pulls the lever up with a thin little cable and when you release the brakes the shoe goes back into place and the lever is spring loaded and pushes the star adjuster around to the next position for another adjustment round the reason it doesn't work when they are way out of adjustment is because the rear shoe never contacts the drum

 

The adjuster is like a sprocket,but the teeth are cut at an angle. Each side goes a diff direction. You should be able to figure it out. They are under the rubber plugs and when you go to do this you can use a flathead screw driver. It is kinda up in there and it's not real easy as just jambing the tool in and moving it around. So be patient. If you want to do it right jack up the rear end, adjust till you lock it up and back off 2 to 3 clicks. You do that and you can pull the e brake at 60 miles per hour and lock em up no prob. It is easy after you get what you are doing.

 

on the star wheel each side rotates top toward you and bottom away
I would jack up one side remove the rubber plug and use a small screw driver and keep turning the wheel as I pushed the star adjuster down untill the shoe just barely makes contact then lower and repeat for the other side
be sure to chock the wheels and take it out of park or gear don't want to get run over by your own truck!