"The miracle does nothing. All it does is to UNdo. And thus it cancels out the interference to what HAS BEEN done . It does not add, but merely takes away. And what it takes away is long since gone, but, being kept in memory, APPEARS to have immediate effects."
What has "been done" is God's will, creation, perfection, the establishing of you as an immortal being, perfect health, eternal life, happiness etc.
But what has been IMAGINED is the ego stuff which has tried to "interfere" with creation. This has produced denial and sickness and pain and suffering and death.
So what the miracle DOES, is that it UNDOES the INTERFERENCES, the ego stuff, so that all that REMAINS is the true-nature of the immortal spiritual self.
Some people interpret this to mean literally "miracles don't do anything". This is a gross error. They actually DO ACT to "cancel" or "reverse" or "dissolve" or "heal" the "strange distortions that were manifest" and wipe them away to RE-ESTABLISH the perfection and health that has been hidden by the ego's interference.
So the miracle actually UNDOES EGO, and therefore UNCOVERS perfection, by REMOVING the manifestations, symptoms, and effects of ego.
Thus they DO produce what appears to be an IMMEDIATE EFFECT. The stuff which is "being kept in memory" is the entire ego thought system, which is dissolved and undone and shone past, to ERASE IT. This produces the "appearance" of transformation even on a physical level.
If we were ALREADY in a state, in time, of perfection, miracles indeed would not DO anything. There would be nothing TO UNDO. But because we HAVE added layer upon layer of ego denial and suffering, THOSE things ARE UNDONE by the miracle, in an ACTIVE way.