select min(percentage) min_perc,
       max(percentage) max_perc,
       count(*),
       sum(cc),
       sum(volume),
       min(volume-cc) keep (dense_rank first order by volume-cc desc) vv, --- ???
       product
from (       
select to_char(rto - rfrom, 'FM9999999999999999') Volume,
       round(cc * 100 / (rto - rfrom), 2) percentage,
       cc,
       product       
from (
select '10000' rfrom, '19999' rto, 100 cc, 1 product from dual union all
select '20000' rfrom, '29999' rto, 5000 cc, 1 product from dual union all
select '10000' rfrom, '19999' rto, 300 cc, 2 product from dual union all
select '30000' rfrom, '39999' rto, 7000 cc, 2 product from dual)
 t
 )  tt
group by product
order by 1 desc