DOT is + or - 1%, by DOT Regulation.
Most scales are less accurate at the low end of their weight range given fixed errors with variable weight to compare. In other words, a postage scale that is off 1/100 oz. because of friction is only 99% accurate when weighing a letter weiging an oz. And, when a 3 pound pagage is on there it goes up to 99.9%. So, if a truck scale has to be 1% accurate when weighing a truck, by regulation, it might be off 800 pounds. Certainly, one would not expect the 1% to apply if one put a 600 pound motorcycle on the scale.
03 Rubicon; 99 xj with too much stuff to list; Unimog 406 (gone)