Entrypoint refers to the identity of a site in a multisite deployment. It is applicable only to RADIUS server configuration ...

Entrypoint refers to the identity of a site in a multisite deployment. It is applicable only to RADIUS server configuration for VPN authentication. It is not applicable to RADIUS accounting and OTP and hence is ignored when a user tries to add a RADIUS server for these purposes

When the parameter is specified it indicates that the RADIUS server for VPN authentication should be added for that site. 

If an entrypoint is not specified in a multisite deployment then the entrypoint to which the server on which the cmdlet is executed belongs is used. The server could also be represented by using the ComputerName parameter

If both entrypoint and ComputerName are specified and the ComputerName doesnt belong to the site represented by the entrypoint then the entrypoint takes precedence and the RADIUS server is added to it