Athens, the Most Awe Inspiring and Magnificent Assembly of Civic Architecture in Greece

Theramenes sends out a call, summoning the athenian assembly. Lysander meets with his triremes once again patrolling athens's harbors and they discuss what to do. A proposal that's been made by one of the party of theAthenian ephors named dracontides asked the athenians to approve a board of 30 men with full powers to draw up a new constitution and govern the city. According to it, theramenes speaks against the proposal. Only 30 men? Why?