The material % should be setup as a calculation in the cube versus a physical column and measure reference. Right now it is simply setup with an aggregation type of sum and that is not what you want. Setup the calculation in the cube and do the division there and you will get the results that you are looking for. You can also setup a calculation in the KPI setup in PPS if needed as well, but having the logic centralized in the cube would be the route to go.