Can you tell if someone has re-read a fb message?

[Anonymous]

I had a fb messenger Convo with my ex the other week and we both saw the convo it said seen Sat 7th feb clicked on the Convo today and it said last seen Wednesday.
Does that mean my ex has re-read the Convo?
I've never seen the time stamp change before.

[shadowlegend]

Does it really matter?