Bubble credits can be used to pay monthly subscriptions - app plans and plugins; it is not possible to use them to pay for annual app plans, templates, perpetual plugin licenses, or coaching sessions. They also cannot be combined with any discounts.
If you have a discount on your account or are attempting to buy an annual app plan, template, perpetual plugin license, or a coaching session, these charges will apply to your payment method on file instead of your credit balance.