Cause the word tariff may be interchanged with other synonymous and related terminology.
A common one that appears in the Georgia resolution is to "protect" or the act of "protection" of industries. This means to enact a tariff that protects a home industry from foreign competition by inhibiting trade.
Accordingly when the Georgia resolution says "After having enjoyed protection to the extent of from 15 to 200 per cent," it is referring to the level of price raised by the protectionist tariff. Other terms to look for are "duties" and "free trade."
A brief history of the rise, progress, and policy of anti-slavery and the political organization into whose hands the administration of the Federal Government has been committed will fully justify the pronounced verdict of the people of Georgia. The party of Lincoln, called the Republican party, under its present name and organization, is of recent origin. It is admitted to be an anti-slavery party. While it attracts to itself by its creed the scattered advocates of exploded political heresies, of condemned theories in political economy, the advocates of commercial restrictions, of protection, of special privileges, of waste and corruption in the administration of Government, anti-slavery is its mission and its purpose.
In contrast the second sentence of the statement says For the last ten years we have had numerous and serious causes of complaint against our non-slave-holding confederate States with reference to the subject of African slavery.
It doesn't even sound like tariffs were a current problem, only that the Republican party had attracted to its side some scattered advocates of a failed protectionist policy. (like Pat Buchanan republicans)
Slavery and the election of Lincoln were the real cause for southern secession, not the abuse of tariffs. And primary sources bear this out.