Why does the AMI come with four EBS volumes?

To ensure compliance with CIS and STIG regulations, we have separated /var, /var/log/audit, and /home out to separate EBS volumes, and have configured /tmp and /var/tmp to be in-memory tmpfs filesystems. You are expected to size these volumes out to fit your specific needs when you create EC2 instances from this AMI. And we assume that your project doesn't have any long-term storage needs in /tmp or /var/tmp. Files kept there will go away on system reboot.