The customizing bundles are assigned to ports in the graphics proxy. However, the combinations of ports and bundles are NOT arbitrary. You must ensure that you assign the right bundles to the right ports.
You have already created an instance of the graphics proxy and of the customizing bundles to be assigned to the ports.
The graphic above shows the business graphics proxy CL_GUI_GP_PRES with it ports. The black dots on the right of the graphics proxy are the ports. The customizing objects CL_CU_DIAGRAM, CL_CU_DISPLAY_CONTEXT, CL_CU_DRAWING_AREA and so on are assigned to the ports.
A display context can be assigned to a port or it can be inside another customizing bundle. The graphic above shows that CL_CU_DISPLAY_CONTEXT can be assigned, for example, to the port Chart or to CL_CU_DRAWING_AREA.
For information on permitted combinations of ports and bundles for business graphics, see the class documentation of CL_GUI_GP_PRES.