Modify the constant combinators next to the displays to edit your item requests. Intermediate products must be greater than their final products (i.e. # of gears requested must be greater than # of belts requested, or # of yellow belts must be greater than # of red belts, etc.). The top combinator is for the foundry, the bottom combinator is for the Assembly Machines.
You can remove the assembly machine if you are belting in Green Circuits.