Stats shown incorrectly For Trailblazer devourer

When you build this item the stats do not show +50% as +40magic damage on hit. The display shows +40% attack speed -10% Cool down reduction. Yet on the passive it still says that you gain a magic damage on hit bonus killing large monster. So i go kill a large monster to get my stack and the stack does show up. It then shows i have +41 magic damage on hit so that means the item is still giving me +50% as and +40magic damage on hit. So the Display is show incorrect stats.