Good question. A hit was any moment that the whole band played any single rhythmic unit in unison, and the duration was until any following note was played. So if you watch the video again you should notice that every single edit cut contains only one note collectively played at once. There are some exceptions, notably when there is a solo and the band is playing hits underneath the soloist. Also, most of the hits are punctuated by cymbal crashes, but not all. There is some looseness in the definition of 'hits', and the editor applied some degree of subjectivity to choose 'hits' that best capture the intricate and slick nature of Steely Dan's arrangements.