What does Judges 9:36 mean?

Gaal saw people coming down from the hills and said to Zebul, 'Look, there are people coming down from the mountain tops.' Zebul replied, 'You’re just seeing shadows on the hills. It only looks like people.' Judges 9:36 - Modern Text Bible

(Gaal is nervous and thinks he sees an enemy force, but Zebul tries to calm him down or mislead him.)