Consider the following two sentences:
(1) She could not care less about him.
(2) She could not care more about him.
On the one hand, (1) seems to mean that she does not care about him at all, so there is no way for her to care less than having the minimum level of care. But (2) could also mean a similar thing, that there is no way for her to increase the low level of care for him.
On the other hand, it seems that we can interpret (2) to mean that she cares so much about him that there is no way for her to care more than having the maximum level of care. But then (1) could also mean a similar thing, that there is no way for her to decrease the high level of care for him.
How do we really interpret and understand these two sentences?