Why did I receive two supplemental tax bills?

If the change in ownership occurs or the new construction is completed on or after January 1, but on or before June 30, then there will be two supplemental assessments. The first supplemental assessment will be the difference between the new assessed value and the taxable value on the tax roll in existence for these dates. The second supplemental assessment will be the difference between the new assessed value and the taxable value on the next year's tax roll.