Rose Heart and Bess Bockstoce are two different peonies. Both lovely in their own right.
I actually called Bannister and she said they manually adjust it and will email or call you with the new total. It confused me as well, because after loading my cart, there were no adjustments at checkout. She said it would have cost them a lot to make the changes occur at checkout, so manually adjusting them made more sense and saved them money, while still providing the discount.