In most real-world situations, numbers are not precise; they represent a range of possible values. For example, the dimensions of a component may have a minimum and a maximum, or an "ideal" value within some percentage.
When you do calculations on these numbers, these errors can accumulate, and if you don't manage them properly, your results will be erroneous. Most calculators can only handle precise numbers; if you want to know the full range of possibilities, you must do all your calculations twice, carefully choosing either the minimum or maximum value for each parameter, depending on how it is arranged in your calculation.
The Crackulator manages them for you. Every number is represented as a range, and all calculations keep track of the maximum and minum possible values. However, for numbers that are exact, it is designed to be just as efficient as any other RPN calculator.