Anywhere from a 3/4 to 2 inches, each truck is different so the drop differs from truck to truck....Also did you tighten up your shackles without th truck in the air????Did you install them wrong, If you did then you wont get a full drop???What shackles did you buy..
You need to jack it back up, loosen them, then tighten them back up once you put the truck's weight back on the ground. Leaf springs are supposed to be tightened up once the vehicle is sitting the way it will normally. You actually preloaded them by tightening it with it in the air.