Hi Rene,
Excellent creation as usual . Please confirm my understanding is correct which is grabbed from this lesson. Please let me know if I am wrong 
General format of MAC address is MM:MM:MM:SS:SS:SS.The leftmost 6 digits (24 bits : MM:MM:MM ) called a “prefix” is associated with the adapter manufacturer.
The rightmost digits (24 bits : SS:SS:SS) of a MAC address represent an identification number for the specific device with the same vendor prefix.
But here in this multicast we use the leftmost 3 octets are (24 bits : MM:MM:MM) always 01-00-5E and the right most digits(24 bits : SS:SS:SS) will be a single OUI (24bits). From this single OUI(24 bits) we use only half of this 24-bits which means 23 bits can be used for mapping 28 bits Mutlicast IP addresses.