8 gig as in description or 4?
It’s 8GB. Updated the title. Sorry about that.
Why limit is 3?
So i can put 4 in my laptop but this limit…
And 4 it is. Buy ALL  of the memory sticks.
It works just for mac or is it compatible with another OS or brands?
Is it compatible for desktop. I want to buy it.
You’d need to look up the information on your desktop to see if it’s compatible.
Note that this is for a Mac.