Why does the third person leave then? Why not number 1? Or number 2? Or all three? Put yourself in the shoes of the fourth person. Don't assume you have the mark, wonder about it. Three people with the mark show up the first day. Then they show up the second day. Why do you assume that they are waiting for you to leave instead of one of them?
and justin if there are three to start with each sees two people with the mark and believes that there are only two sinners so thy should stop coming in two days so they all come back on tuesday and realise that there have to be three people with the mark