If you have a machine that can be setup in different configurations depending on the quantity being processed, this can be modelled by using the same resource as alternatives but specifying different setup and run times for each, e.g.

In the above example, the same resource is being used in each of three alternatives (A Drill), but its throughput is different in each case. In this example the higher the throughput the longer it takes to set. This means for any particular quantity to be processed there is an optimum setup. Specifying the alternatives as above, allows the planning system to find and choose the optimum.