Your NG Firewall is generating and sending out its daily email reports. Depending on the amount of data in your reports, that can be quite resource-intensive!
NG Firewall may also be generating and uploading a cloud backup via the Configuration Backup application (if you have it running).
Your NG Firewall is also rotating out its syslog and database tables at this time.
The short version is it's normal to see that small usage spike and shouldn't be cause for alarm.Follow