Message Characteristics in Process Data Calculation Formulas 
A process data calculation formula must contain the following message characteristics:
All required characteristics of the requested message category
All optional characteristics which are to be included in the message
The definition of the message characteristics directly follows the corresponding message category in the process instruction.
How you need to assign the message characteristics to the process instruction depends on the way in which they are to be processed, that is, whether their values are to be assigned:
In planning
Automatically in the PI sheet
Manually in the PI sheet
You can define the message characteristics in any sequence. However, the process instruction characteristics pertaining to a message characteristic must be defined in the sequence described in the corresponding section below.
Message Characteristics: Value Assignment in Planning