@Riot about the new Bond of Stone Mastery

So this mastery would provide +4% Damage Reduction. While near an ally this bonus is doubled and 8% of the damage they would take from champions is dealt to you instead (cannot reduce you below 15% Health).

So how that work? what if i am around 4 allies this thing would stack up for 4x8% damage reduction? and i would take if they have an AOE ability that hit all 4 people 4x8% of the damage that hit them?

This is how that thing work?