The order shall:
(a) Describe the land entitled to a special rate of assessment or the respective parcels of it if separate parcels are to be assessed.
(b) Fix the proportion of the regular rate of assessment which shall be applied in levying assessments on the land described or on each parcel of it if various parcels are found to be entitled to different special rates in order that the assessments to be levied on this land will be proportionate with the benefits which it receives or will receive from the operations of the district.