The Server tab page allows you to set characteristics of the time server function of the Windows Time service.
The Time Server section allows you to specify whether the Windows Time service will act as an NTP server.
The Reliability Flag section lets you change how Windows Time indicates the reliability of the time being served.
"A computer that is configured to be a reliable time source is identified by time clients as the root of the Windows Time service.
The root of the Windows Time service is the authoritative server for the domain and typically is configured to retrieve time from an
external NTP server or hardware device. Other time servers can be configured as a reliable time source to optimize how time is
transferred throughout the domain hierarchy. If a domain controller is configured to be a reliable time source, the Net Logon service
announces that domain controller as a reliable time source when it logs on to the network. When other domain controllers look for a
time source to synchronize with, they select a reliable source first, if one is available."
--- from How to configure an authoritative time server in Windows Server 2003
The Net Time Flag section lets you determine if Windows Time will announce itself as a LanMan time server.