Look at these links. Anyone who can read a tape measure can see clearly that there is more than 1/2" offset in those shackles.
http://www.summitracing.com/parts/DCC-4120075/
Look at how the brackets are made. Yes, the studs ARE 1/2" offset compared to stock, however, the brackets are made so that they offset the rest. Look at how the bracket walls are offset as well. You cannot measure just the offset of the studs that hold the bracket on. You have to measure the entire amount, including the offset of the bracket itself. They move the spring inboard exactly what MP says they do. I have measured it enough that I can do it in my sleep.
http://www.summitracing.com/parts/dcc-4120077/applications/