I have a part from which I want to produce a mold. I have made all necessary surface bodies manually and have made the tooling split successfully. At this point, all I need is to make a core coming perpendicularly to the mold opening direction. I want to use the "Core" function in SolidWorks, but when I follow the steps I get a core which cuts through the whole mold, even though I select the "Up to next" option. I just want the core to match the surface of the cavity.

Can anyone guide me further from this point?