When a field can be null, it has what's called a "Null Indicator". During debug of an RPG IV program that contains fields with Null Indicators, displaying the field's content does NOT show you the setting for it's null indicator.
The EVAL debug command, however, can be used to display the content of the Null Indicator. It also shows you the field's current contents. Here is the syntax:
Debug . . . EVAL _QRNU_NULL_myField
Where myField is the field name whose NULL Indicator is displayed.
_QRNU_NULL_ is the null indicator prefix for the field.
_QRNU_NULL_myField would be used to show the value for the null indicator for the field named myField.
The field's contents is also displayed when its Null Indicator (NULLIND) is displayed.