Only one I know is for radio reception 'receiving you 5 by 5'
Meaning modulation or sound quality 5 out of 5 (max) and signal 5 out of 5. Both on a scale of 1 to 5. Simply, perfect audio and signal.
It's radio jargon . . . two catagories of measuring Volume and Tone - 0-10 equals weak to very loud and 0-10 means too mjch treble vs too much bass - therefore 5:5 means perfect volume and tone.