Demantra - Using is_fictive to prevent disaggregation to a certain combination in a worksheet

In Demantra, Is there a way to use is_fictive to prevent disaggregation to a certain combination in a worksheet?  This attribute is described in the implementation guide, in the proport section.The proport mechanism considers only real combinations. That is, it ignorescombinations for which is_fictive equals 1.I have tried setting this value to 1 on mdp_matrix, but forecast is still being disaggrated to the combination.am I missing something, or is is_fictive not used by the disaggregation process?