whittle something down
phrasal verb with whittle verb [ T ] uk/ˈwɪt.əl/ us/ˈwɪt̬.əl/
使缩小；使（人数）减少
to gradually reduce the size of something or the number of people in a group
We had 80 applicants for the job, but we've whittled them down to six. 这个职位我们有80位申请者，我们已经将其筛减到了6位。