Skyrim enchanting effects question

Hey, I was enchanting some gear earlier to give me a better alchemy score so i had 4 things which gave me a +20% each so shoould that equal 80%??
its just i didnt notice any difference between when i had them on and when i didnt??

What is the ecnhangtment effect? It would only be 80% if it's the same spell, and I think it lumps it together. I don't know, I don't enchant much, I'm more of an Alchemy guy lol.

Also I never do smithing, so boring to me.

it was alchemy is 20% better..So i thought they all went together but the strenght of the potions didnt change or if they did it was a very very small change..