(a) In L33T speak, "cool cool" is used as acknowledgement for absolute understanding, no further discussion on the matter is necessary, as in "So we're not going to play beer pong? Cool cool. Let's do keg stands."
(b) Kk also means, "cool cool", also means "ok, cool'
(c) "cool cool" also means "I get it, and that's cool."
"Cool cool. What time do we leave?"