What does this icon mean?

Here's a list of some icons and references to understand what they mean:

sending-18x12.png Sending
sent-18x12.png Sent
delivered-18x12.png Delivered
read-18x12.png Read
disappearing_countdown.gif Disappearing Messages
reply.png Quoted Reply threads for Android
secret_sender_20.png Sealed Sender
view-infinite-24.png Media can be viewed more than one time.
view-once-24.png View-once media message
viewed-once-24.png View-once media message, viewed 
select-24.png Select
link-broken-16.png Set up an iPad as an independent device or unlinked device.
contact-circle-outline-32.png Contact is saved to your phone's contact list.
note-24.png Note to Self
check-24.png Safety number has been marked as verified.

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