Simple Quick Questions(about buttons and inspector)

I have two questions;

1. Should I worry about the variables in the inspector? like collider size(x,y) they always seem too long like "0.824886". would this cause any kind of performance issue. after putting so many objects with colliders, should I normalize them?

2. When I put an image in front of a button(little transparent light). the button doesn't seem to be intractable because of the image in front, how can I solve this.