In the example marked on that picture, 30 degrees has been used and a 40 knot wind. The line is drawn down to the 40 knot arc, then straight down for the crosswind component and across for the headwind, 20 and 30 respectively.
In the other example "If there is a wind on runway 03 reported as 350/25, what is the crosswind component?" The angle is 40 degrees (the difference between 350 and 030) and wind strength 25 knots. So trace down the 40 radial till you get to the 25 knots arc, then straight down for your crosswind component of about 16 knots.