At the conclusion of the hearing on the resolution of intention and of the hearing, if any, upon proposed modifications, the board may by resolution order the improvement district formed for the purpose and with the exterior boundaries described in the resolution of intention, or for the purpose and with the exterior boundaries as proposed to be modified in the resolution, if any, proposing modifications. Said resolution ordering the district formed shall state the estimated expense of carrying out the purpose described therein. Said resolution shall also number and designate said improvement district substantially as “Improvement District No. ____ of ____ District.”