Tim Nice, did you enable trace log for the business rules to see if there are any errors while processing this MATH statement? Location of the logconfigtoolexe: C:\Program Files (x86)\BMC\Service Desk Express\Tools. Enable trace in the dropdown against NAMMBL by selecting this option. The debug view tool should give you details around what's getting processed.
Thanks for the suggestion, I will try that and see what debug shows.