Said board of appraisers shall have full authority and it shall be its duty to determine the percentage of benefits which the acreage of the lands in each class shall have with respect to the lands in class No. 1. Those lands falling in class No. 1 shall have the ratio or percentage of one hundred and those lands in the other respective classes shall be given such percentages of the lands in class No. 1 as said board of appraisers shall determine.