Hello Ankush
This issue has to do with the way we read the OSPF database. Specifically, each LSA has a Link ID and an Adv Router that are shown in the table. These fields do not show the actual destinations being advertised but identify the LSAs exchanged between the OSPF routers.
The ADV router is the router ID of the router that advertised that particular LSA. In your case, looking at the OSPF database of R3, your loopbacks are contained within the LSAs that have the ADV Router of 192.168.20.1. This IP address is the router ID of R1. This can be confirmed by the fact that you have a link count of 4 (three loopbacks and one physical link) for that router.
As an aside, in your case, the router used the highest IP address on an interface to define the router ID. You have loopbacks as well, but those must have been added after the router ID was established. (if you reset the OSPF process, your router ID will change on R1 based on the OSPF router ID selection process).
For LSA type 1, the Link ID is the same as the ADV Router column. However, for type 2 LSAs, the Link ID refers to the router ID of the DR on the segment.
The point here is that you won’t actually see the destination networks within the OSPF database on the router with this command. In order to see the actual contents of the Type 1 LSA, you must use the show ip ospf database router command, which will show you details of the Type 1 LSAs that the router has received.
For more info no how to read the OSPF database, take a look at the following lesson:
I hope this has been helpful!
Laz