Not a number.
For use as a general fill value or for non-logical results.
If a ratio is relevant only in forecasted periods due, use @na for other periods. For example:
@if(@ishist, @na, v1400/ v2890)
where Total Interest Expense is v1400 and Total Liabilities is v2890.
N/A* X= N/A and N/A+ X= X