Hello! Thanks for your interest in my game!
To be honest, I’m just the developer, so I don’t have direct insight into the purchase system. However, this page should explain how the buying process works:
https://itch.io/docs/creators/how-buying-works
If you’re still unsure or run into any issues, I recommend reaching out to itch.io’s support team. They’ll be able to help you further. You can contact them at support@itch.io.