Those shocks will only adjust the preload (stiffen or soften) 1 is softest 5 is stiffest. The preload basically just controls where the shock rides in its stroke by controlling how much your weight and the weight of the bike compresses the bike when you sit on it. If it is set to 5 then your weight will not compress the shock as much and the higher it rides in its stroke. If you set it to one then you get the opposite, your weight will compress the spring more making it ride lower in its stroke. Ideally you want it ridding in the middle of the stroke as determined by setting the SAG.

These shocks are not going to raise or lower the bike to any real noticeable level. Obviously if you are a heavy guy and you have it set to 1 then once you sit on the bike the springs are softer and it will sit lower under your weight. However the shock will be riding low in its stroke you will hit the bottom of the shock on each bump and your ride will be shitty.

As a side note not sure of the shocks on your bike now but the ones pictured pretty much look like the shocks that would have came on an 09 Street Bob

 

Mxdad layed it out for you the best.
Keep in mind the Pre-load affects the way the bike handles, really soft and the rear end just kind of drags along while in a corner,(like it's dead), too hard and the rear tire will want to bounce or skid out in a hard corner.
Pre-load is about the carry/load weight of the suspension that still allows the shocks to do what they're supposed to.
Nothing to do with "height".