Postgres listens on random port

I have a scenario in which postgres listens on a random port different from the one which was specified in pg_ctl start command.

This occurs in windows. When postgres is started on port 5460, the logs denote that postgres is started on 5460. But the database actually listens on some random port like 20011

When the same postgres is started as a service,it listens on the intended port.

I have tried with both normal and admin users.

Any suggestions on this behaviour will be helpful. 

Regards 

Kal