When I pull up my messages, some of them have a white dot by them?

[iMore Question]

When I pull up my messages, by a couple of them is an odd little dot. It's white and grey, to the right of the message. Like before you click on the messages and it has everyone you're texting in a list? It's only by a couple. It's not notifying me of anything, if my message isn't read there's usually a blue dot instead of a white one.

 

[Reparkable]

It's not a new message?
Screenshot?