I just bought a Korg Pitch Black (like everyone here recommended )
but I don't know what kind of adapter I should use. In the manual it says the pedal needs at least 600 mA, but on the pedal itself it says the maximum is 200 mA. Can anyone tell me what's the correct amount?
What the manual says. The pedal will draw as much current as it needs from the adapter. If the adapter is capable of handling 600mA and the Pitchblack only needs 200, it'll draw 200. You won't fry it if you use a powerful adapter.
Ignore the manual. What's on the pedal is important. Manual writers are notorious for cutting and pasting the wrong info.

If power requirements are printed on the pedal it should be the correct information. Printing a requirement under the actual rating would open Korg up to liability issues.