In context, it almost looks like a ratio like " 5 to 5", so it could be 5 and 5, like two hands, i.e. hand-to-hand combat? It seems like the 5:5 is related to a threat, "As the World Turns", etc...
Just a thought.
5:5
5 by 5 is military jargon for a good, strong signal
It used to be a common phrase when communicating by radio. “I hear you 5 by 5.”. Same as saying “I hear you loud and clear.”
So I think he is just saying the message was loud and clear.
Signal strength & readability ratio
5:5 = Loud & Clear
From old style radio comms
Signal strength = 5
Readability = 5
When used in that context, asked as a question (5:5?) at the end of a statement, it can be interpreted like this,
Bagster
5:5 is radio lingo. On a scale of 1 to 5 you have two categories. Signal-strength and Readability(How clear). With 5:5 being the best of both. So 5:5 means loud and clear.