The cryptocurrency market is well known for being volatile and big fluctuations are a part of it.
In some cases, the exchange rate of the cryptocurrency might change from the time the payment was initiated till it was finished, meaning that you would receive less cryptocurrency than you saw in the checkout page.
However, it is not possible for you to receive less than it was displayed in the checkout without your confirmation. If the change is significant, we always inform our users with an email regarding the changes in the rate and total amount and they can proceed accordingly - accept them or cancel the transaction.