GO reports a warning when the disk space on server falls below 1024M. There are 2 properties responsible for enforcing the limits, 'db.warning.size.limit' and 'artifact.warning.size.limit'. These values are not related to the purge start and purge end limits. These limits can be changed by overriding the values of these properties.
In case of linux, set it in GO_SERVER_SYSTEM_PROPERTIES environment variable in /etc/default/go-server .