Straigt -vs- Crooked border in Southern Egypt

I get out my encyclopedia today and look at the artical for Egypt. The map shows the southern boundry of Egypt and says National Boundry and it is straight across to the red sea.

Now on that same map it say Administrative bountry and just before it gets to the sea the boundry goes up north a bit like this _______
/
_______/

Why two boundries?

All the maps I’ve looked at have the border jogging north-east to the Red Sea. My guess is that Egypt could do whatever they wanted with their southern boarder. Sudan has neither the resorces nor the international support needed to contest the issue. Does anybody know if there’s anything worth “administering” in the Nubian Desert?