"Incalculable power"

[zanooda2]

Here is one more question, what does "incalculable power" mean in a sentence: "Dumbledore had at least taught Harry something about certain kinds of magic, of incalculable power of certain acts". It's when Harry tries to convince Ron that he is supposed to use the sword, p.373-374 or p.304 ("The Silver Doe"). 

Does the word "incalculable" mean here "uncertain, unpredictable", or does it mean something like "immense"? The dictionaries give these two meanings, but they both seem to fit. Or do I misunderstand something :-)? What do you guys think? Thanks,

zanooda