Glad you figured this out !
From my undestanding of Dynamo, there is no iterations here, only parallel computation : you could have done each operation seperatly, without taking the other into considerations. It is like if you had two lists ( say [1,2,3] and [4,5,6]) and asked a team of smart guys and gals (metaphor for Dynamo) to compute the sum of the two lists. This team would work in parallel and three people would have done the calculation : a first person would compute 1 + 4, and second one 2 + 5, and a third one 3 + 6. Ultimately they would gather to form the result ([5,7,9]), but no one had any access to the inputs of his or her buddies.
To be honest, I never got the thing with<1>, <2>, etc, but it definitely has something to do with lacing haha 