RAM slots reported 4 slot, but found only 2

As the title says. Laptop: NP300E5C-A07US

So once before I hackintoshed, I saw 4 reported slots. After my motherboard was replaced, Speccy reported 4. As I have 2 extra Hynix RAM, I tried to install both, but only found 2 slots. One already has a Samsung 4 GB.

Where's the last 2?