Deliberate mistake: At the end fight scene, when they are in the barn one of the men falls crashes through the wall when they get hit, spilling the fight to the outside. Unless the barn's walls were made of cheap plywood, the wall would not have given away so easily. Obviously done for dramatic purposes.
Continuity mistake: When the "fight" starts and they crash through the restaurant window, the lady who stands and screams on the left, does so twice as the camera angle changes.
Revealing mistake: It's obvious that when Clyde disassembles the car, the car has been pre-disassembled so Clyde would have an easy time taking it apart. Specifically the doors and trunk lid.
Continuity mistake: When we see Clyde demolishing Patrick Scarf's Cadillac, we see Clyde tapping the roof of the car. In the next shot from inside the car, the whole front of the roof is being caved in, but when we see Clyde tapping on the roof again, the roof is back to its original shape.
Visible crew/equipment: When Clyde is demolishing Patrick Scarf's Cadillac, he is using both hands to hold up the front windshield. In the next shot, you can see a crew member wearing an ape glove to help Clyde move the windshield.
Chosen answer: This means 70%, ie. for every dollar they are owed they will only recieve 70 cents.