If a project is using reclaimed greywayter and rainwater stored in a cistern to flush toilets in a building how would one properly account for that on the LEED Indoor water use reduction calculator?

My understanding of the credit intent is to reduce potable water usage in the building. If that's the case, for flush fixtures in the calculatore can the user simple enter '0' for the Design Flush Rate since no 'potable' water is being used for the flush fixture operation?