CreditCheckingService SOAP Webservice - AvailableCredit = Credit Limit + Tolerance ?

I have question to be clarified for AvailableCredit

I observed that when invoking the Credit Checking API to retrieve the available credit for a customer, the returned value appears to include both the customer's credit limit and credit tolerance.

For example:
Created a new customer with Credit Limit = 15000 Credit Tolerance = 10%
No sales orders have been created for this customer.There are no open AR invoices or credit exposure associated with the account.

However, the CreditCheckingService SOAP API is returning an Available Credit value of 16500

Based on this result, it appears that the API may be calculating Available Credit as:
Available Credit = Credit Limit + Tolerance Amount