runnic armor Mastery

8 % bonus to all shields and healing on you (includes lifesteal and regeneration).

when i have 12 % lifesteal and have this mastery then it shows 13% Lifesteal dats ok.

but when i buy bt and have 350 schield at lvl 18.. it doenst show 350 *8/100= 28 28+350 = 378!!!

how should i trust this mastery now for increasing schields ????

it also doesnt show dat my e as riven has incresed schield.....

on lifesteal it shows but on schield it doesnt....

i cant trust this

bad tooltip design