DHCP requests are relayed only if their SEC field is greater or equal to the threshold value in order to allow local DHCP Servers to answer first.
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