Cooldown VS Attack speed?

[Jaina Proudless]

Hello, I want to make a research that decreases the cooldown of my unit from 4.0 to 3.8.
But the research says it "increases attack speed" and uses a percentage.

So I really don't know how these two work together. What percentage do I have to put in to set the cooldown of my unit to 3.8?

 

[Flux]

Attack speed

 

[Jaina Proudless]

I don't play dota 2.

 

[Xonok]

Most mechanics in dota 2 are identical to WC3, because DotA was originally made here.
Anyways, for turning 4 to 3.8 you can just do 4/3.8 to calculate the difference. This gives about 1.05, which is 5%.