Debug Information

When I'm on a column of a grid, I don't see the Table and the field of that column when I ask for the DEBUG INFORMATION which is located in the lower left corner of SAPB1

For instence, I can see the 4 first column information like "Form=, Column= and then OIGN, Dscription"

when I try the 5th I dont see the table and the field as mentioned above

I presume its a calculated column but where do I go to see how SAP does the calculation ?