What does Macbeth's use of paradox in line 149-"cannot be ill, cannot be good"-indicate about his frame of mind?

Macbeth's dialogue "cannot be ill, cannot be good" reflects his state of a dilemma about the three witches' prophecy. He notices that something which the witches have prophesied has come true. He says that though these words are true still they have negativity in them. When he considers them a good one, he feels terrified about the murder of King Dunken which he committed after listening to the prophecies. And when he considers them a bad and evil prophecy, he thinks about the promotions he had achieved after it.