A negative credit balance usually happens when a purchase is refunded through the App Store or Google Play. When a refund is processed, the credits from that purchase are automatically removed from your account.
If those credits were already used, your balance may go below zero.
How to Fix a Negative Balance
Purchase additional credits to restore your balance to zero or higher
Once your balance is positive, you can continue using all app features normally
Important Note
Refunded purchases always result in credit removal, and this may affect your current balance if the credits were already used.