Each formula needs to be carefully considered and written to ensure that it can be interpreted by Fireworkz and that it provides the correct answer. You can, for example, write a formula which Fireworkz understands and processes, but produces a result different to that which you intended.
If you are performing an operation which requires more than one function, split the work across several cells. This ultimately gives you more control over your work, and makes it easier to avoid mistakes.
See the following for help with formulae: