I'm rather confused by the word "cool" these days. Back in the sixties, saying "cool" was cool but by the seventies, it was absolutely uncool. Now that it's been back for a few years, it seems to be used for virtually anything. When I speak with my 19 year-old son and his friends, "cool" crops up continuously and randomly.
Son: What time is it?
Me: Ten past two.
Son: Cool.
I'm guessing that the meaning here is either "okay" or "thanks".
Me: How was your night out?
Son: Really cool.
Presumably, this means "great".
Me: If you're going to be late tonight, take your key.
Son: Cool.
I believe this is shorthand for "I understand".
I'm cool, me.