Question how does Extra damage get applied on sheids

[:1]I have found a 55%extra damage Royal shield 4os with 121 AR. How does the extra damage get applied?

does it only work if used as a smiter?

does it work with a aura from the shield?

or does it get applied across the board.|||Across the board, so to speak. It sums with other equipment and skill-based enhanced damage (and strength) which applies to both Smite and skills like Zeal/Charge/whatever. It does not directly increase the damage of the shield by 55%.