xxx of enchanting

ok. i tried searching for this, but i only get a list of auctions upon auctions. i wanted a bit of clarification on the "... of enchanting" mod, if anyone knows.

does it affect enchantments cast on you or enchantments that you cast?

for example, let's say i have a weapon with a mod that lets enchantments last 20% longer. obviously, if i cast an enchantment on myself, it will last 20% longer. however, let's say someone else casts an enchantment on me. will that last 20% longer? or will an enchantment i cast on someone else last 20% longer?

If only affects enchantments that *you* cast.