Changing the size/dimensions of a button's bounding box

Okay, I edited all the images so that they’re only 75px by 75px, re-uploaded them, and reassigned the button textures. But the problem persists. I’ll keep trying to monkey around with it, but it looks like I haven’t accomplished much.

I guess I’m assuming that my problem is being caused by the bounding box being too wide. If that’s the case, then this is what I want to do: