Saves for Vitriolic Sphere (CA) ?

[Tarril Wolfeye]

How are the Saves for Vitriolic Sphere supposed to work? It seems as if you get your first save just for negating the secondary damage and saves for half damage are just when you would get secondary damege. The text is just not clear for me. Any help please?

 

[shilsen]

As written, here's how I see it working (let's assume the caster is 10th lvl):

1 - All affected creatures take 10d4 acid damage. If they make a Ref save, they take no more damage. If they fail, move to 2

2 - One rd later, affected creatures that failed the first save takes 6d4 dmg. If it makes a Ref save successfully, it takes half dmg and the spell stops affecting it. If it fails the Ref save, move to 3

3 - One rd later, affected creatures that failed the second save take 3d4 dmg, with a Ref save for half dmg.