Field help (ADPNIVDEF) 

The definition level is used to characterized the deepest level of detail possible to associate a value for each parameter. If, in a given context, no value exists at the defined level, ascend up successive levels until a value is found. It is therefore possible to define a default value for the levels above the bottom level of the definition, in order to only manage the specific cases of the lowest level.

The definition levels possible, defined by the local menu 987, are, in descending order :