No, do not pay attention to fxsniper's post.
The puzzles are in the bits/keyspace related to the amount.
Like you said, #64 (.64 BTC) is in the 64 bit range: 8000000000000000:FFFFFFFFFFFFFFFF
Thank you for the clarification. As the public key is not available for some of these puzzle transactions some will need to be brute-forced using the base58-check address right?