Why can I use Apple Pay when buying something when my Apple Pay has four dollars

Hi Latishakid

welcome to the Apple (user-to-user) Community.

Re: Why can I use Apple Pay when buying something when my Apple Pay has four dollars

Apple Pay uses debit and credit cards in Apple Wallet to transfer $ to pay merchants and websites.

(There is generally no balance held in Apple Pay as it is not an account.)

The payment method(s) in your Apple ID account are used for all purchases from Apple.

Seems your $4 may be in your Apple ID Account balance ?

How to: Check your Apple Account balance - Apple Support

(In some countries you may be able to add Apple Pay as a payment method to your Apple ID):

Check which payment methods Apple can accept in your country or region:

Payment methods that you can use with your Apple ID - Apple Support

If needed: How to add an Apple ID payment method:

Add a payment method to your Apple ID - Apple Support

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To see what purchases you can make with an Apple ID Account balance:

See: What you can buy with your Apple Gift Card or Apple Account balance - Apple Support

Eg: Article says: "Some purchases might require that you have a credit card on file,

even if you use your Apple Account balance to make the purchase".

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You may want to check if there are restrictions set on purchases from the App store:

Eg: Manage App Store purchases, subscriptions, settings, and restrictions on iPad - Apple Support

or

Check with parents whether parental controls are in place that restrict in-app purchases.

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If you wish: You can check how in-app purchases work:

How to: Buy additional app features with in-app purchases and subscriptions - Apple Support

Hope there is something in here that helps you :-)

All the best :-)