Most Recent Date -- what does it reflect?

Question - see the screen shots below. It shows a post with a "most recent date" of September 23. However there are several updates/posts within the thread that are later. The example shows them dated Oct 4th and Oct 5th. The screen shot is a composite of the main screen view and two of the posts within the thread.

My assumption is that the "most recent date" should reflect the date of the most recent post within the thread.

--- Is this correct?

--- Or there another process for updating the "most recent date" ?

--- Or is this just a glitch in the database?

Regards, Al / NN4ZZ