Why some messages still say "Delivered"

[AC Question]

I've been texting someone recently and I've noticed the read and delivered status indicators next to my messages. I assume this is the advanced texting feature. But I only see these when texting this one person. Sometimes It says the time next to it when it was sent with not notification. Sometimes it says "delivered" and sometimes "read."

My question is....sometimes a message will still say "delivered" when other subsequent texts have turned to "read." So if the recipient has read a text message they must have read the one before it too, right? I'm just asking because I don't think this person is getting all of my texts.

 

[ManiacJoe]

The reading of message B has no relationship to the reading of message A.