The process or template contains a form field (in either a task form or a launch form) whose field type is Number.
The value submitted for this field must be a string that contains a number, e.g.:
However, a non-numerical value has been submitted for this field. For example:
Possible Causes and Suggested Actions
The data in the field is of the wrong type. It is supposed to be a string that contains a numerical value. However, it is something else. The value needs to be replaced with a valid value.