The error: The paragraph from the executive budget is tied to an example where property values increase by 20%.
Take the district with 22 effective miles, of which 4 are inside. The 20% increase applies to the 18 outside mills only, reducing the effective rate from 18 to 15.
But, wait. Add the 15 outside mills to the 4 inside mills and you end up with only 19 mills -- below the 20-mill floor. So the effective rate cannot be reduced the full 20%.
This means that there is a tax increase in this district -- those mills do grow.