A expression primarily used by people who don't know the difference between weight and volume, it's supposed to mean that the situation is "fucked up" or "out of control". A better phrase would be "10 gallons of shit in a 5 gallon bag", but the person using the phrase is too fucking dumb to know the difference.
-"Fuckin. . .everything is crazy at fuckin work right now. It's like trying to fit 10 pounds of shit in a 5-pound bag, nothing works
-5 pound bag. . .like a bigass duffel bag? That could probably hold like 80 pounds of shit, so you should be good.
-No, fuckin, 10 pounds but only 5 pounds so there's shit everywhere.
-Like you have a 1 pound brain in a 10 pound head?
-Exactly, you're retarded."