iOS / iPadOS Multiple Billing

Apple can group multiple purchases in onto one bill.

When you buy items or pay for subscriptions, your payment method is charged at the time of purchase or within a few days.

If you don’t recognize a charge, try to identify that charge in your purchase history and see if multiple purchases were grouped onto one larger charge. Or look at the receipt that was emailed to you and see if multiple purchases were included. If you use Family Sharing, both the purchaser and the family organizer will receive an email receipt.

Here is more information about it from the official Apple Support.