How does razer gold confirm to the buyer that the gift card it sells has not been used?

As the agent seller of google play, you can't check whether the product you are representing is valid at the time and whether it has been used, so how can we consumers confirm? It can be understood that buying a code that is easy to use is considered good luck. Is it bad luck to get to the used code? Because no one has any way to check the usage time of the code.