If many shipments or points of origin or destination are involved in a proceeding in which reparation is sought (See § 502.63), the Commission will determine in its decision the issues as to violations, injury to complainant, and right to reparation. If complainant is found entitled to reparation, the parties thereafter will be given an opportunity to agree or make proof respecting the shipments and pecuniary amount of reparation due before the order of the Commission awarding reparation is entered. In such cases, freight bills and other exhibits bearing on the details of all shipments, and the amount of reparation on each, need not be produced at the original hearing unless called for or needed to develop other pertinent facts. [Rule 251.]