Newbie Question: Magnified effect only 15%?

[ManRammer]

I am not the best of players, so I have likely misunderstood something. I just socketed "Magnified effect" (+40% AoE) into the skill "Lightning Rod" for the Ranger.

But when looking at the data for the skill the AoE of it only increased from 2 meters to 2,3 meters (+15%) instead of 2,8 meters (+40%).

Is it bugged or am I misunderstanding something? Thanks for the help beforehand :)