My other screenshot was not very good to explain the issue here, let me make a more detailed explanation of the issue.
The issue is not entirely identical but, it IS very much related so yes, this place was the correct place to post it.
Before your post a detailed explanation, there's no need for it. Right now, GSX doesn't really know about exact measurement of the plane internal cabin so, ULD/Pallet loading is made using a generic calculation based on fixed distances that don't change by airplane.
Doing it right, would require having to configure exactly for each plane those data. And, we'll probably need to add extra data to know exactly how many containers of each type can fit, which would be even more complex when mixing up different types of pallets. That would probably justify a completely separate add-on dedicated only to cargo operations.
Again, everything's possible, and everything's noted for possible future updates.