These fields are hidden by default, and I think it is a bug that they can be made visible at all, and that they are editable.
I believe the fields are not used at all. Qty on Order is the technical name of the field normally called Pegged Qty in the client, and I don’t think a supplier material line can have peggings. Operation No would be the operation which to the material line is connected, but that is not used for purchase order material lines either (just shop order material lines).