One possibility... according to Lisa Mei Crowley on Twitter (@LisaMei62), 5:5 in radio terminology means “Read you loud and clear.”
That’s quite an open ended language form.? Hard to describe 5:5.LOL
Yes, in the world of radio communications, that is true. Good signal strength, good clarity. In the old CB radio days, we used to say "hittin' me with a full 10-pounder, good buddy" referring to the signal strength meter on the CB radio showing full signal strength. Old technology, coupled with "trucker" slang for all of us wannabe cool geeks.
Have seen Q use that a lot so that must be what it means.