Speaker arrangement terminology

The first number is on the floor plane.

The second is the number of subs

The third number is overhead.

So a

5.2.4 would be 

5 floor speakers

2 subs and

4 overhead speakers

again 

5.4.4

5 on the floor

4 subs and

4 overhead..

so a 

20.10.20 would be a bunch of work.. ;-)

11.4.4

11 floor speakers

4 subs

4 overhead speakers

AGAIN

9.10.8

9 floor speakers (even the front center speaker is under 4 feet and can be a much larger speaker than the mains) It is actually how HT is suppose to be.. The center speaker is the MAIN speaker... VOICES, especially whispering...

10 subs (location or how it's driven does not matter)

8 overhead speakers (corners and sides BUT on TOP)

The only real choice after that is "Speaker Size" that cuts the mains at a certain point and can add a step up  on the BASS side for the subs.. LFE (step baffle) vs left right full signal. They are a very different way to power subs..