The specs say "- Direct Link (Only 1 Cable Needed)" so I'm going to assume it's a single USB-C interface. I did buy it here instead of their website since they seem reluctant to give answers, and I feel like Drop's return policy is going to be better than going direct.
Edited: In hindsight, I decided not to order this thing at all. I just bought an external super narrow profile display and will somehow adhere it to my main keyboard. Best of both worlds and I don't need to wait for these people to actually answer real questions.