340 xhead spring shimming, height and pocket question(s)

Thanks for chiming, I understand the coil bind, but confused with how shimming increases installed height? Shims lower it correct? Or are you talking the combination of taller retainers and shims?
He is stating to use offset or "raised" retainers, which will increase the ht., maybe more than needed. You would then shim the seats to the desired ht.