Spell Dmg%

I have a pretty complicated question to word so Ima try my best :P

Straight up question
Does - spell dmg % effect your spells?

More explanation :P
If I have a -50% spell dmg item will it minus the DAMAGE I do with a spell OR does it negate +% Spell DMG I have on an item?

(remember there is no silly question only silly answers :p)

 

This may seem a little complex:

These equations are using 10%=100 damage, which is just an EXAMPLE.​

Say you have 60% spell dam, which does x amount of damage with, say, meteor spell.
Say x is 600
Then you get a -50% spell dam, making you lose 500 damage (y=500)
x-y=result damage
in the end, you have 100 damage.

I hope this makes sense.

I'm pretty sure the staff aren't THIS evil, but it's a possibility:

As before, 60%=600 damage
-50%
BUT this time -50% it means -50% of 60%, which makes 30%
Outcome this time is 300 damage.