It doesn't matter if your ex had his own status. You applied to sponsor him. This will come up in any invitation you send.
It's not at all clear to me that there is an error. You say that his extension was granted to December 2018, and that this was the date mentioned in the notes. What exactly do the notes say? Is there a chance this date is in the notes as the expiry date of the extension?
Then say that in your application. But be aware that you can say this and still have the right to sponsor him - you cannot write your way out of that right. And since you did attempt to sponsor someone else once, this is a risk in your profile.