Question with Percent Health runes

Sometimes when I play I just want to have a ton of health so I have a rune page that consists of 9 percent health seals and 3 percent health quintessence resulting in 9% health. My question is pretty much how does this interact with the items I buy, my masteries like the juggernaut mastery and thats about it. For example does the 9% health add up to 11% with juggernaut mastery? In game does the 9% health do its math after purchasing items? With cinderhulk is it 9% max health than 25% max health?? Thanks a lot for answers