Why Bungie, why would you do this?! - Halo Community
The circled alphanumeric code 6EQUJ5 describes the intensity variation of the signal. A space denotes an intensity between 0 and 1, the numbers 1 to 9 denote the correspondingly numbered intensities (from 1.000 to 10.000), and intensities of 10.0 and above are denoted by a letter ('A' corresponds to intensities between 10.0 and 11.0, 'B' to 11.0 to 12.0, etc.). The value 'U' (an intensity between 30.0 and 31.0) was the highest detected by the radio telescope, on a linear scale it was over 30 times louder than normal deep space.[1] The intensity in this case is the unitless signal-to-noise ratio, where noise was averaged for that band over the previous few minutes.
I just copied that from the your wiki page link.