When you add a new payment method to your Microsoft account, a small temporary authorization hold may be placed on your card to verify that the payment method is valid. This is not a percentage of the game's price, nor is it an additional purchase fee.
After this verification, Microsoft will attempt to charge the full price of the game. If the temporary hold reduces your available balance and you no longer have sufficient funds to cover the purchase, the transaction may be declined.
The authorization hold is normally released automatically within a few business days, depending on your bank or payment provider. It may simply disappear from your transaction history rather than appear as a refund.
If the amount remains pending beyond your bank's usual processing period, I recommend contacting your payment provider for clarification.