Instrumenting the server means preparing the server for advanced Admin4 editing by providing a LDAP entry to store configuration data. When instrumented, the configuration is stored in an Admin4 specific entry with the dn cn=<Admin Entry RDN>,<Ldap Base DN>. The Admin Entry RDN value can be configured using the Admin4 Preferences/LDAP settings and is preset to Admin4ConfigData which will probably be collision-free in any LDAP environment. This entry shouldn't be edited manually but using the Configuration dialog only.
When you're using LDAP as SAMBA2 backend, you most probably need to configure the ID generation style, so you should instrument the server in any case.
The server's instrumentation status is displayed on its property page.
After the server has been instrumented, any Admin4 client can retrieve site specific configuration data from it.