In ShooterGame why do some variables update on editor change but others only when the source is rebuilt?

In ShooterGame, for the WeapLauncher blueprint for the launcher weapon, I can update ProjectileLife in the editor but it doesn’t actually change the life of the projectile when I run it. It only changes it if I change the defaults in VS and rebuild the entire project.

But for AmmoPerClip, I can change the value in the editor and it’s reflected immediately.

Why are these variables (ProjectileLife, ExplosionDamage, ExplosionRadius) even in the editor if they’re not able to be changed?

I hope someone will answered you very soon. I am very new on Unreal. But for c++ for Unreal in general, i re-command you to fallow this tutorial: