In figure 2, it is clearly illustrated that user B is exposed but the corresponding texts mentions that B and D do not get exposed.
Figure 2 illustrates the effect (and benefit) of proximity tracing. C is infected and diagnosed COVID-positive. User A gets notified and become "at risk" users. A gets tested and is diagnosed COVID-positive. B is in turn notified, becomes "at risk" and is confined before meeting D. Consequently, B and D do not get exposed, and therefore infected, anymore.
In figure 2, it is clearly illustrated that user B is exposed but the corresponding texts mentions that B and D do not get exposed.