[Oscar in Batangas]

It can go either way...

“Couldn’t care less” is pretty straightforward,

BUT

“Could care less” implies total lack of caring squared. I.e. I don’t even care enough to care less.

So:

I could care less, but I don’t even care enough to care

[Windflier]

“Could care less” implies total lack of caring squared

Not in English, it doesn't.

You're saying you have the capacity to care less than you do now.

On the other hand, "could not care less," says that you have reached the absolute minimum level of caring.