Actually, I think his question is why does the system identify one DL code as a RedILTee and another as RedEOLTee, which has nothing to do with the button mappings in his Setup Services?
I do not think this is well documented but my understanding is that the system is analyzing the duct sizes in your routing and it has determined that the 20x20 (80 inch perimeter) running into the 24x12 (72 inch perimeter) is a RedEOLTee. One big duct with two smaller ducts coming off at the end. In the case of your 24x24 running into two 24x24 ducts, it stays as a RedILTee.