The total amount is used only to determine if the calculation should be included in the calculation, and is not used to determine the deduction amount.
The amounts that show on the bottom of the deduction when you open it from an employee records are not exclusive to the year we are currently in. It shows the total number of periods and total amount of money withheld for the life of that deduction.
NOTE: The total amount of the deduction will include historical entry entries. However, it will not include these entry amounts in the calculations for 'Stop deducting when the deduction exceedds XXX $XXX" Therefore, the deducation could appear to exceed the limit. Reduce the amount to not exceed by the amount on the historical entry.