Asymmetric confusion

[eugene rabii]

So I've looking at the JMH samples and pretty much all of them were 
somewhere clear to me until I reached asymmeteric and using groups.

I'm looking at the example here :

http://hg.openjdk.java.net/code-tools/jmh/file/5d6eee917c11/jmh-samples/src/main/java/org/openjdk/jmh/samples/JMHSample_15_Asymmetric.java

And the first important comment starts with this:

"make two execution groups, each having 4 threads"

*two*? I can see just one that is called "g".
So each method that is annotated with @Group is an "execution group"? 
And by default it runs in 4 threads?

Sorry if this is a newbie question, but I simply don't get it.

Thx, Eugene.