What are the names of the top 8 countries by total invoice size and what are those sizes?
return countries ;return total invoice sizes of #1 ;return the  8 highest of #2 ;return #1 where #2 is equal to any of #3 ;return names of #4 ;return #5 ,  #3
['select', 'project', 'aggregate', 'comparative', 'project', 'union']