Hi

I assume C has states space 0,1,2,3,4. In this case each configuration of A and B maps to the state of C. The you should read the potential as illustated below

((( 1 0 0 0 0 ) % B=0 A=0 - C is in state wih index 0 (i.e., C = 0)

( 0 1 0 0 0 ) % B=0 A=1 - C is in state wih index 1 (i.e., C = 1)

( 0 0 1 0 0 )) % B=0 A=2 - C is in state wih index 2 (i.e., C = 2)

(( 0 1 0 0 0 ) % B=1 A=0 - C is in state wih index 1 (i.e., C = 1)

( 0 0 1 0 0 ) % B=1 A=1 - C is in state wih index 2 (i.e., C = 2)

( 0 0 0 1 0 )) % B=1 A=2 - C is in state wih index 3 (i.e., C = 3)

(( 0 0 1 0 0 ) % B=2 A=0 - C is in state wih index 2 (i.e., C = 2)

( 0 0 0 1 0 ) % B=2 A=1 - C is in state wih index 3 (i.e., C = 3)

( 0 0 0 0 1 ))); % B=2 A=2 - C is in state wih index 4 (i.e., C = 4)

Each vector is a probability distribution over the states of C. As C = A+B this corresponds to a deterministic function where C is "instantiated" to the state corresponding to the sum of its parents.

This fits with the explanation.