Can anybody tell me where to set the wideness of these 2 panels?
As you can see on the right side it's just empty space. That's why I wanna shorten that away.
 

Goto the 
"Docks": {
section and in bottom left, change the width there.
If you only have the clock in that one though, ideally, just change the background color to all 0s. It will just remove the box entirely. Looks much cleaner.

Setting background colour to 0 fixed it in both cases. Thank you.