Let me give you an overview of how endurance works since its pretty important to understand early on. The core idea is that your health gains only count going forward, so whatever endurance you have right now is what determines future level-up bonuses. Maybe interesting, but starting with high endurance around 65 gives you way more health per level compared to starting low at like 30 - were talking about 3.7 versus just 0.3 health points each time you level up.

The way the math works out, if you wait too long to boost your endurance, youll end up with about 100 less health by the end of your playthrough which is pretty significant when youre in tough fights. The system uses this floor division thing where it rounds down your gains, so getting those early endurance increases really makes a difference for your overall survivability. Definitely something to think about during character creation and those first few level-ups if youre planning for the long game.