In this section, “total rate of tax” means the rate of tax imposed for the agricultural land transfer tax under § 13–303(a) of this title plus the rate of tax for a county transfer tax imposed under this section. Unless a greater rate of tax was imposed before July 1, 1979, a county may not impose county transfer tax on a transfer subject to the agricultural land transfer tax under Subtitle 3 of this title at a rate greater than the county rate applicable to the transfer of improved residential property in that county. If a county has imposed a county transfer tax at a rate that exceeds the rate applicable to the transfer of improved residential property, the total rate of tax that applies to a transfer subject to the agricultural land transfer tax may not exceed 5% plus the rate that applies to improved residential property under the county transfer tax. If the total rate of tax that applies to a transfer subject to the agricultural land transfer tax exceeds the maximum rate allowed under paragraph (2) of this subsection: the agricultural land transfer tax is payable at the rate specified in § 13–303(a) of this title; and the rate of the county transfer tax shall be reduced as necessary to comply with the 5% limit. After July 1, 1979, for the transfer of land subject to the agricultural land transfer tax, a county may not: impose a county transfer tax at a rate above the rate that was in effect on July 1, 1979; or increase the rate of a county transfer tax above the rate that was in effect on July 1, 1979.