This is a Lua modification which shows the current HP of the boss which you are currently facing. Also, in stages when you have a Guard Bonus (but not in Splitscreen) you can also see your own HP in regards to the Guard Bonus:
6HP (Green): Full Guard Bonus
5-2 HP (Yellow): Some Guard Bonus
1HP (Red): No Guard Bonus
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6HP (Green): Full Guard Bonus
5-2 HP (Yellow): Some Guard Bonus
1HP (Red): No Guard Bonus
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