It sounds like a way to exaggerate net weight lost.
Let's say you're a man of average height and slightly overweight , 5'9" and 190 lb, and you want to drop 30 pounds. You lose the 30, start your crappy eating habits back up again , gain 20 and then catch yourself and lose another 20 to get down to 160.
Technically, you lost 50 lbs, but it's a net loss of 30, so 30 is the figure you would tell everybody.
In Hamberlynn's case, it would be binging to 550 6 months ago, and then calculating her January weight loss from the highest figure so it looks like she lost 66 rather than 16 pounds.