In your dynamic value of the element that is doing the math operation place this suffix on the end of the dynamic value statement, For Example:
(number1 * number2 - number3).toFixed(2)
This will remove the digits following the second digit on the right side of the decimal. If you would like to display 3 digits on the right side of the decimal simply change the function to this: toFixed(3)
If you would like to go higher or lower change the number to suit your needs.