"Blocked only"
The "blocked only" selection in the upper panel on the Locks tab (in Session Browser) will show only the sessions that are being blocked by something else. To find out who is blocking it, you will need to select that session, then look at the panel below where it has 2 tabs "blocked locks" and "blocking locks". The panel below and the tabs are dependent on what you choose at the top. If you choose a session at that top that is a "blocked" session, then you should look at the panel below, select the "blocking locks" and it will show what session is blocking it.
"Blocking only"
The "blocking only" selection in the upper panel will only show the sessions that are blocking something else. To find out what it is blocking, you will need to select that session, then refer to the panel below. Since you are looking at a session that is session "blocking" something, then you should look at the panel below, select the "blocked locks" and it will show what session is being blocked by it.
