The purposes, estimated cost, amount of bonded debt, or boundaries shall not be changed by the board except after notice of its intention to do so, given by publication pursuant to Section 6061 of the Government Code in at least one newspaper published in the district. The notice shall state the changed purposes and the estimated cost and debt proposed and that the exterior boundaries as proposed to be changed are set forth on a map on file with the secretary of the district, which map shall govern for all details as to the extent of the proposed improvement district or districts, and specify the time and place for hearing on the change or changes,

which time shall be at least 10 days after the publication of the notice.