“I couldn’t care less” means that “I really don’t care about it.” A similar expression is, “It couldn’t be worse”, which means “It is the worst situation.” Therefore, in this case, “I couldn’t care less what he says” means, “I don’t care about what he says.” In another case, if you answer that, “I couldn’t care less.” when someone asks you about your ex, it means that you do not care about them at all. However, many people mistakenly say, “I could care less.” This has a contrary meaning to the intended meaning.

L.L.F editor-in-chief You-Jin Kim