LeaseEnd is specified as number of seconds since midnight (00:00:00), January 1, 1970 and defines the time at which this particular IP address expires.

LeaseEnd=1198953446

This entry is automatically created by the DHCP Server.
Lease times are important when a client requests an IP address and all addresses in the IP pool are already assigned to other clients. In that case the client whose lease time (LeaseEnd) has expired least recently is deleted from the INI file and the available IP address is used for the request.