Brandon,
Thanks for the quick reply. I'm using version 3.5.177 of Survey123 on my cell phone. On the XLSForm I have set the default to 0 for these fields, however all these fields/questions are conditional, only appearing on the form when the answer is 'yes' on the previous question.
The issue caused by these null values is that when any of the 4 calculation fields I have on the XLSForm encounters an empty value, it returns NaN as a result. I must be doing something wrong, I have just recently started using Survey123 Connect instead of the web designer.
Please find form attached.
Thanks,
Martin