Grasshopper split brep sort

hi I want to cut bunch of breps and pick out the area of the box inside

so i used split brep, it seems breps are cutted when baked but i dont know how to sort inside

The panel shows two pieces of data.
How should this be classified?

You could test if the centroid of the resulting surfaces are contained inside the box:

Thanks it helps me a lot

could you advise me when split brep with surface?

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