CK custom AOE spell problem?

[blacksupernova]

I tried to add stagger effect to Firestorm spell using CK. To do that I copied an existing Stagger effect from MGEF and set area to 100. Then I added the effect to the spell, the Area section in the Effect info window was gray, meaning I can not change it. Nevertheless, CK showed the effect had 100 area. But when I tested in-game, it staggered nothing but me. Using TESsnip to look again and I saw the area section was still 0, changing it to 100 using TESsnip resulted in what I had expected. So am I using CK right or there's something wrong with it?