If a district is located in more than one county, the total estimate as provided for in section 48-2411 shall be divided by the board of directors in proportion to the value of the real property included within the district in each county. This value shall be determined from the equalized values of the last assessment rolls of such counties. When the division of the estimate has been made the board shall furnish to the boards of supervisors and county assessors of the respective counties a written statement of that part of the estimate apportioned to that county.