Hi Akav,
Thank you for reaching out to us. You can obtain credits using the field totalAdjustments under BudgetOrder, which will come in the form of credits or debits to your budget order. For more information about adjustments, please see here. Please let me know if you have further questions.
Thank you,

If you're on the manual payment setting, you'll make a payment for your Google Ads costs before your ads run, and that payment will be used to pay for your advertising costs once your ads start running.
You'll do this each time you want to add money to your Google Ads account, and whenever the money in your account starts getting low, we'll send you an email reminding you to make another payment.
Here's what to keep in mind as you make payments on this setting:
Hi Akav,
Thank you for the clarification. Through the API the remaining credit field is not directly accessible via API. However, you can compute the remaining balance by subtracting the total Cost of the Account Performance Report from your known budget. This should give you the remaining balance. Please let me know if you have further questions or concerns.
Hi Akav,
In the case that your Automatic Budget account is set to unlimited making the subtraction impossible, then unfortunately it is not possible to obtain the remaining credit, as remaining credit is not directly accessible by API. Please let me know if you have further questions.