Sforno on Exodus 18:21/ספורנו על שמות י״ח:כ״א

1ואתה תחזה מכל העם, select, and then appoint. The only area in which you alone are competent is the choosing of suitably qualified helpers, in accordance with the guidelines Yitro outlined. When it came to handing down judicial decisions, however, there would be 78600 appointees of four different levels of competence who would deal with all but the most perplexing problems without having to come to Moses for approval of their rulings. Initially a problem would be submitted to one of the 60000 men appointed as “chief” of ten. If such a man did not know the answer he would refer it to one of the 12000 chiefs of 50, and so on in an ascending order. The different levels of judges would in effect act as appellate judges, reviewing if judgments made by the lower ranking judges and appealed should be changed.