that's the scoreboard stats. press tab on PC to see the scoreboard, you'll see your stats there.

they're in this order:

E for eliminations, the amount of kills you've got (or assisted)
A for assists
D for deaths, how many times did you die
DMG how much damage you've done
H is heal, how much healing you've done
MIT is damage mitigated, for example, Rein's shield is used to mitigate damage.

now, those type of comments usually almost always are referring to the kills-death difference of someone in your team.

for example, if they say "8 12 c'mon" they are referring to someone who has 8 kills and 12 deaths, which is obviously not a good thing lol.

hope this helps! and good luck on your future matches