Looks like they're the ones for the expansion slots, which come iirc in 250gb and 1tb options. The ports are modular, and you could forgo one (or three) say USB ports and replace them with memory (or ethernet, SD, MicroSD, HDMI, etc.) And swap them around at will.

Idk what is inside the cards, but there are files out there to 3Dprint a shell for one that can take the guts from a USB thumb drive to act as the same thing, which I'm gonna print soon enough.