Must be a multiple of 2
Since workers can return an assignment or drop out, some "spare" participants will be created: the oTree session will have 2 times more participant objects than the number you enter here.
Your app description
This implements trust game with a funky way of matching. A player plays both the role of the proposer nad that of a responder. A proposer is matched to a responder by selecting one player from a 10 randomly selected player. When he plays responder, the same process is followed: 10 players are drawn randomly and one player is drawn from those players.