When the flash file which is used by reports becomes full, a certain percentage of the old messages on flash are deleted. This is the current value.
Sources for this description
Multiple manufacturers; see the original MIB MIB copies (LibreNMS/Observium Community)Dell MIB copies (LibreNMS/Observium Community)Netdisco MIB archive copiesNETGEAR official product and EOL MIB downloads