Billing can sometimes be confusing in iTunes, as Apple often combines multiple purchases to one transaction and charges for them at the same time. In case you have made multiple purchases from the game or some other app within a few days, then you might have been charged for all these purchases at the same time. In addition, the charge can appear on your bank statement a few days after the purchase has been made.

When in doubt, please check your purchase history on iTunes to see if this explains the issue, and see the following Apple Support page for further information: https://support.apple.com/en-us/HT201382