With calculations in binds it is easy to run into NaN (Not-a-Number) or INF values showing on the form.

There are few ways to get rid of them

- You can use if inside the calculation to prevent the calculation from running if the inputs would result in NaN or INF.
- Use the relevant attribute in your bind expression to hide the field if the value is not numeric. You should be able to use something like not(number(myNode)) as the condition.
- use the xxforms:format attribute together with translate to simple translate NaN and Infinity values to empty strings.
<xforms:output .. xxforms:format="translate(translate(., 'NaN', ''), 'Infinity', '')" />