if nothing else changed on the 1099-div that means non-qualified dividends ( the difference between total dividends and qualified dividends) went down by an equal amount
filing an amended return probably would result in some tax savings but without knowing your tax situation no one can say how much. your choices are to either open up the 2018 return (not the amended link) enter the revised figure to see how much you would save and then make a decision as to whether to file an amended return or not. (there is no requirement to file an amended return if your taxes go down) then put the number back to where it was so you'll have no problems with AGI when doing 2019) or use the amended link to see. if you do not choose to file the amended return, you have to delete the changes.
while no one can say what your actual tax savings would be, if you know your tax bracket then multiply it by the $133. that would be the max.
