Subtracts nodes by rolling them up to the same set of levels (intersect). The result has the coarser level of each shared dimension of the input nodes.
Node1 - Node2
The Subtraction works exactly as the opposite operation to the addition.
We recommend to add all costs as negative values, hence you will not need the subtraction often.
5-2 = 5
|2018||10-(3+4) = 3|