How Does a Higher Confirmation Requirement Mitigate a Double-Spending Attack?

A confirmation is a block added to the blockchain after the block containing a transaction. Each subsequent block makes it exponentially harder to reverse the transaction, as an attacker would need to rewrite the chain from that point.

By requiring more confirmations (e.g. 50 instead of 6), the exchange ensures the transaction is buried deep in the chain, making a successful reversal via a 51% attack prohibitively expensive and unlikely.