The UI doesn't properly read combo damage exceeding the length of the life bar, because it doesn't know what to do with it.
If you hit 300 points of damage or more in one combo, then yes, it is a kill combo (at least using the default health bar settings). If you tried it in a real match (which is usually pretty difficult to set-up with these types of things), the opponent would die at the end of the combo.
I'm used to the bar resetting when you go over 299 or so, but when I checked to see how close I was I saw 300 anyway a video will be out soon. If Eliot feels like cooperating
If you hit 300 points of damage or more in one combo, then yes, it is a kill combo (at least using the default health bar settings). If you tried it in a real match (which is usually pretty difficult to set-up with these types of things), the opponent would die at the end of the combo.