+X% defense means that your hero’s defense stat is increased by X% when the damage source is red. That increased defense is used in the damage calculation. So damage is reduced, but not reduced to 0.
What I understand is, the display +175 defense is come only from +32% defense (Turn left: 1) = Costume Melendor.
And those elemental defense does not count in the display, because it is only applied from red, not all color, so it means, the defense against RED is hidden.