Albert Barnes Commentary Judges 8:14

"And he caught a young man of the men of Succoth, and inquired of him: and he described for him the princes of Succoth, and the elders thereof, seventy and seven men." — Judges 8:14 (ASV)

The written list would enable Gideon to punish the guilty and spare the innocent people. Succoth was governed by a sanhedrim or council of seventy elders , with perhaps seven others of superior rank called princes.