I am using Jitsi 2.0.6865-2 version own server and I am having the same issue that when a user leaves, the notification shows "user1 and user 2 left " where only user 1 is left and user 2 is still on call. Also sometimes shows the wrong name when the user left the meeting
That sounds like a bug that was fixed a while back.
You version is rather old, and bugfixes are not backported to older versions so you will have to upgrade to benefit from fixes.
If you cannot upgrade you jitsi version, then the only option you have might be to fork Jitsi-Meet from that version, fix the bug, and deploy your custom Jitsi-Meet to your deployment. Or disable that notification in config – no information often better than wrong information.
But frankly, in the long run it will be easier to make sure you can upgrade to latest Jitsi version since browsers change all the time and you will need latest Jitsi to stay compatible.