The Signal messenger and protocol.

I sent a message at 1:06pm and didn't hear back or message them again afterwards. Then around 5 pm I received this as a signal notification even though we weren't in the same location or messaging at the time.

I opened it and the verified/safety number is now permanently at the bottom of all of our messages.

I don't recall ever setting up a safety number with this person, but if I did it would have been like a year ago. Why would this suddenly pop up now?