فيكون الدهن بمثله والزيادة بالثجير
Translation: The oil corresponds to an equal amount of oil, and the additional amount corresponds to the residual pulp.
Thajir refers to the residual pulp or press-cake after oil extraction. The expression al-ziyadah bi-l-thajir means that the excess extracted oil is assigned in exchange for that residual matter, rather than counted as an excess against the embedded oil.
This is not a device of simply renaming countervalues. The real components of each side, their lawful value and the embedded ribawi part must be identified. An unexplained excess cannot be legitimized by labeling it as something else.