Shocking Grasp Question (in General)

I'm sure this has been asked and answered before, but I haven't been on the forums much so I don't know.

In the DD wiki, under SG, it says "1% extra damage for each point of base AC on the opponent."

Does this mean the HoC will reduce SG by 5%?

in the past jon has stated that a negative will usually be read as zero by game mechanics, so i highly doubt it.

The ACs are probably added up before the damage bonus is calculated.

Therefore, the -5 will decrease the damage of SG by 5%, but only so far as the total base AC remains positive. A negative base AC is most likely treated as 0, just like negative ST, negative DX, etc.