Portrait packages are designed around the number of subjects being photographed, and the number of images desired, so it's actually not complicated at all.
When you don't need a lot of 4x6 proofs, they can be exchanged for other sizes, and here is the exchange chart:
two 4x6 proofs = four wallets (same image)
three 4x6 = one 5x7
five 4x6 = one 8x10
ten 4x6 = one 11x14