Under Suppl/Cust/Main you will see the supplier or customer code, if it is a purchase or customer order, respectively. If it is a manufacturing order you will see the customer code or the user who registered the manufacturing order (if there is no customer code). If it is a material requirement, you will see the main part number for the main part that incorporates this part. If a suggestion origins in the Run Netting procedure this will be indicated by the word RunNetting in the column. If the suggestion origins in the Requirement Calculation procedure this will be indicated with the words Req. calc. in the column.
You can select the row in this column, to either replan orders or view additional information by right-clicking and opening the Info menu.