hmm... I've seen this from somewhere else

I can't remember which option this was
and sc doesn't exist in my comp so I can't check it either
but it's most likely to be [Units & Hero settings]
like in the image, you choose the most bottom Unlabled/Unused
and increment the number to 100.
(which number? dunno really... the guy who wrote the tutorial didn't leave any specific names of what refers to which. try it out urself. theres only 2 anyway -.-a)
The original psi storm damage is 14 per 1 hit, but after incrementing,
it'll be 100+14, thus 114 per hit so the total damage would be like
892 or 1006... (don't remember clearly...) That should do it.
Edit : The image is sorta squished. -_-; (or is it just me?)
You'd have to click it to view normally