What does this feature means and how does it works?

What does “Crypto Rewards: Earn rewards in different crypto currencies” means and how does this works? It is visible in the comparison list for Black and Metal accounts.
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Crypto Rewards are an entirely new product enabling Curve premium (Black and Metal) customers to switch the type of cashback they earn to cryptocurrency tokens, with the Curve X tier, only being able to earn Crypto Rewards in Bitcoin.Find out about upgrading your subscription here

Crypto Rewards is an opt-in feature, totally exclusive to our premium customers. If turned on, it allows you to earn crypto tokens both on your Curve Rewards offers, as well as on purchases eligible for 1% Curve Cashback with 3 or 6 selected retailers for Black and Metal customers.

See more here: Crypto Rewards