Hey! So sorry for not seeing your response sooner!
It's just how the busses take inputs. You wire from the input pin to the pin on the bus line you want it to use, and it will make the wire disappear, with a red dot on the input pin to let you know it's hooked up!
Here's a link to this project's files so you can try the chips out for yourself! (Be careful, the big storage chips can be pretty laggy!)
https://drive.google.com/drive/folders/1izAIND0fSJdlHVHxr_yGPsGMboNPWQWl?usp=dri...