"50% of Your Total Character Defense Added as Vitality"
So, if your total character defense is 300k, u get 150k hp? If not the case, it definitely needs rewording.
The only other scenario I can imagine is this: you have gear and MOs that give xx% to Total Character Defense. And this chest takes 50% of whatever that number is and gives you it as Vitality. Which is low. AF. Probably not even 1k.