Question about the Monster Formation Wiki

Hello, I would want to have more information about Monster Formations. I've read the Wiki, but it seems a bit unclear to me still.

It says that the first four bits of byte 1 is VRAM map. Is it the "mould" that I remember seeing in FF3usME? (I can't use it as I'm on Linux and it doesn't seem to work with Wine. Also, I'm too lazy to create a virtual machine only to run that.) Also, what is the MSB Monster Index? Finally, how does the unused " Monsters Loaded to BG1 (unused)" works? Thanks in advance!