Abiter of Ash is not increase difficulty HP=5M alway

I have leveled up the Boss-related passive skill tree atlas to 10 points, but when I beat the boss Abiter of Ash using the Red Key, the boss's HP is still 5M alway The boss's difficulty has not increased even after leveling up the Boss's passive skill tree atlas. please help me

Oh, I get it. The boss initially has more than 5M health, but if we die, it will reduce to 5M health. That's my fault, not a bug.