Looks like you need to request an SLA credit manually:
<a href="https://support.google.com/cloud/contact/cloud_platform_sla" rel="nofollow">https://support.google.com/cloud/contact/cloud_platform_sla</a><p>Details:
<a href="https://cloud.google.com/compute/sla" rel="nofollow">https://cloud.google.com/compute/sla</a>
As an AWS user, it's amazing to see a status page show an actual status. Curious how many of these posts there would be if their status pages were accurate.