S.U.M. has nothing to do with math, the initials stand for Set Up Marked.

It is the stacked, marked deck that needs no calculation or memorization whatsoever because the deck does all the work. You don't have to decipher esoteric markings to remember formulae, everything is literally spelled out for you.

The deck appears to be in completely random order.
There is absolutely no calculation or memorization required.
Can also be used as a normal marked deck.
The instructional manual contains six effects and routines using the S.U.M. deck, although many more are possible and limited only to the imagination.