Symptoms: The built-in Math element is used to evaluate an expression at runtime, but the resultant value is stored as either -0 or NaN.
Resolution: A value of -0 can occur with negative numbers in expressions that would normally evaluate to 0. This is not an error condition and can be handled by any custom code or decisions your application uses to parse this value.
A value of NaN means that there was a problem with the evaluation of the specified expression. For example, division by zero would result in a value of NaN. Whenever your voice application uses the built-in Math element, it must check for this value and handle it appropriately, for example, exit down a math_error exit state from a Decision element so that the call flow can continue.