The First Empress Cygnus Defeatd in KMS

No you're wrong. No HP bar works like that in any game, ever. If HP bars go over the set length, then all games have a x3 or something that means "It has this much HP left x3" Once that hp bar goes down, it fills up back to full and says x2, etc

Really, I don't know where people come up with those kind of theories -___-

Those x4 HP bars you brought up are EXACTLY why I came up with that theory.

When Wizet first programmed boss HP bars, they probably didn't anticipate giving a boss (Or at least the part of the boss that gets the HP bar.) 2 billion+ HP, so they probably didn't design the bars to hold that much HP. And they might have not wanted to add "x10" for some reason. (It is a pretty stupid system. Especially when different bosses have the same number of bars but not even close to the same amount of HP.)

Of course, I wouldn't rule out the possibility of actually having her heal herself to artificially extend her HP if the game's programming won't allow an individual mob to have more than 2100000000 HP.