Game Theory in Practice: HEM red line
Now let's recall how the red line works in sngs. For each hand in which two players are all-in, an "EV diff" is computed. The hand EV diff equals the difference between the expected ICM payoff over the allin outcomes, and the ICM payoff of the outcome that actually occurs (so it will be negative when you are "lucky" and positive when you are "unlucky" with respect to ICM). If no two players are allin in a given hand, the hand EV diff is 0.
Thats the best I can help. I've always ignored this type of thing because I found a lot of players are looking for a reason they are 'running bad'.
Seems like a decent explanation though.