In order to receive any of the Financial Credits described above, Customer must notify Google technical support within thirty days from the time Customer becomes eligible to receive a Financial Credit. Customer must also provide Google with server log files showing loss of external connectivity errors and the date and time those errors occurred. If Customer does not comply with these requirements, Customer will forfeit its right to receive a Financial Credit. If a dispute arises with respect to this SLA, Google will make a determination in good faith based on its system logs, monitoring reports, configuration records, and other available information, which Google will make available for auditing by Customer at Customer’s request."
From that linked page:
"Customer Must Request Financial Credit
In order to receive any of the Financial Credits described above, Customer must notify Google technical support within thirty days from the time Customer becomes eligible to receive a Financial Credit. Customer must also provide Google with server log files showing loss of external connectivity errors and the date and time those errors occurred. If Customer does not comply with these requirements, Customer will forfeit its right to receive a Financial Credit. If a dispute arises with respect to this SLA, Google will make a determination in good faith based on its system logs, monitoring reports, configuration records, and other available information, which Google will make available for auditing by Customer at Customer’s request."