If Ann is assigned the type \(t_1^A\), then she considers it possible that Bob believes she will choose \(u\). Notice that type \(t_1^A\) has a 1 in the row labeled \(t^B_1\), so she considers it possible that Bob is of type \(t^B_1\), and type \(t^B_1\) believes that Ann chooses \(u\) (the only places where 1 appears is under the \(u\) column).